diff --git a/modules/aggregations/src/main/java/org/elasticsearch/aggregations/pipeline/BucketSelectorPipelineAggregationBuilder.java b/modules/aggregations/src/main/java/org/elasticsearch/aggregations/pipeline/BucketSelectorPipelineAggregationBuilder.java
index 2271bbe44d3f5..1d8934a26251f 100644
--- a/modules/aggregations/src/main/java/org/elasticsearch/aggregations/pipeline/BucketSelectorPipelineAggregationBuilder.java
+++ b/modules/aggregations/src/main/java/org/elasticsearch/aggregations/pipeline/BucketSelectorPipelineAggregationBuilder.java
@@ -48,7 +48,7 @@ public BucketSelectorPipelineAggregationBuilder(String name, Map<String, String>
      */
     public BucketSelectorPipelineAggregationBuilder(StreamInput in) throws IOException {
         super(in, NAME);
-        bucketsPathsMap = in.readMap(StreamInput::readString, StreamInput::readString);
+        bucketsPathsMap = in.readMap(StreamInput::readString);
         script = new Script(in);
         gapPolicy = GapPolicy.readFrom(in);
     }
diff --git a/modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/GrokProcessorGetAction.java b/modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/GrokProcessorGetAction.java
index 633b8d1986901..adaf7e0d6c4d7 100644
--- a/modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/GrokProcessorGetAction.java
+++ b/modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/GrokProcessorGetAction.java
@@ -98,7 +98,7 @@ public static class Response extends ActionResponse implements ToXContentObject
 
         Response(StreamInput in) throws IOException {
             super(in);
-            grokPatterns = in.readMap(StreamInput::readString, StreamInput::readString);
+            grokPatterns = in.readMap(StreamInput::readString);
         }
 
         public Map<String, String> getGrokPatterns() {
diff --git a/modules/ingest-geoip/src/main/java/org/elasticsearch/ingest/geoip/GeoIpTaskState.java b/modules/ingest-geoip/src/main/java/org/elasticsearch/ingest/geoip/GeoIpTaskState.java
index c924c19210f44..b5024c7c0f8ec 100644
--- a/modules/ingest-geoip/src/main/java/org/elasticsearch/ingest/geoip/GeoIpTaskState.java
+++ b/modules/ingest-geoip/src/main/java/org/elasticsearch/ingest/geoip/GeoIpTaskState.java
@@ -67,10 +67,7 @@ public static GeoIpTaskState fromXContent(XContentParser parser) throws IOExcept
     }
 
     GeoIpTaskState(StreamInput input) throws IOException {
-        databases = input.readImmutableMap(StreamInput::readString, in -> {
-            long lastUpdate = in.readLong();
-            return new Metadata(lastUpdate, in.readVInt(), in.readVInt(), in.readString(), in.readLong());
-        });
+        databases = input.readImmutableMap(in -> new Metadata(in.readLong(), in.readVInt(), in.readVInt(), in.readString(), in.readLong()));
     }
 
     public GeoIpTaskState put(String name, Metadata metadata) {
diff --git a/server/src/main/java/org/elasticsearch/ElasticsearchException.java b/server/src/main/java/org/elasticsearch/ElasticsearchException.java
index abf13b2c23dbb..9b32e04b43e6a 100644
--- a/server/src/main/java/org/elasticsearch/ElasticsearchException.java
+++ b/server/src/main/java/org/elasticsearch/ElasticsearchException.java
@@ -145,8 +145,8 @@ public ElasticsearchException(String msg, Throwable cause, Object... args) {
     public ElasticsearchException(StreamInput in) throws IOException {
         super(in.readOptionalString(), in.readException());
         readStackTrace(this, in);
-        headers.putAll(in.readMapOfLists(StreamInput::readString, StreamInput::readString));
-        metadata.putAll(in.readMapOfLists(StreamInput::readString, StreamInput::readString));
+        headers.putAll(in.readMapOfLists(StreamInput::readString));
+        metadata.putAll(in.readMapOfLists(StreamInput::readString));
     }
 
     /**
diff --git a/server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/DesiredBalanceResponse.java b/server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/DesiredBalanceResponse.java
index 3ffade0159b92..28760cdb0d209 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/DesiredBalanceResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/cluster/allocation/DesiredBalanceResponse.java
@@ -61,7 +61,7 @@ public static DesiredBalanceResponse from(StreamInput in) throws IOException {
             in.getTransportVersion().onOrAfter(CLUSTER_BALANCE_STATS_VERSION)
                 ? ClusterBalanceStats.readFrom(in)
                 : ClusterBalanceStats.EMPTY,
-            in.readImmutableMap(StreamInput::readString, v -> v.readImmutableMap(StreamInput::readVInt, DesiredShards::from)),
+            in.readImmutableMap(v -> v.readImmutableMap(StreamInput::readVInt, DesiredShards::from)),
             in.getTransportVersion().onOrAfter(CLUSTER_INFO_VERSION) ? new ClusterInfo(in) : ClusterInfo.EMPTY
         );
     }
diff --git a/server/src/main/java/org/elasticsearch/action/admin/cluster/shards/ClusterSearchShardsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/cluster/shards/ClusterSearchShardsResponse.java
index f627eafab447e..9c127b6360f90 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/cluster/shards/ClusterSearchShardsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/cluster/shards/ClusterSearchShardsResponse.java
@@ -30,7 +30,7 @@ public ClusterSearchShardsResponse(StreamInput in) throws IOException {
         super(in);
         groups = in.readArray(ClusterSearchShardsGroup::new, ClusterSearchShardsGroup[]::new);
         nodes = in.readArray(DiscoveryNode::new, DiscoveryNode[]::new);
-        indicesAndFilters = in.readMap(StreamInput::readString, AliasFilter::readFrom);
+        indicesAndFilters = in.readMap(AliasFilter::readFrom);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/GetSnapshotsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/GetSnapshotsResponse.java
index 91b1740777d82..251d2976dac7a 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/GetSnapshotsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/GetSnapshotsResponse.java
@@ -94,7 +94,7 @@ public GetSnapshotsResponse(
     public GetSnapshotsResponse(StreamInput in) throws IOException {
         this.snapshots = in.readImmutableList(SnapshotInfo::readFrom);
         if (in.getTransportVersion().onOrAfter(GetSnapshotsRequest.MULTIPLE_REPOSITORIES_SUPPORT_ADDED)) {
-            final Map<String, ElasticsearchException> failedResponses = in.readMap(StreamInput::readString, StreamInput::readException);
+            final Map<String, ElasticsearchException> failedResponses = in.readMap(StreamInput::readException);
             this.failures = Collections.unmodifiableMap(failedResponses);
             this.next = in.readOptionalString();
         } else {
diff --git a/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/shard/GetShardSnapshotResponse.java b/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/shard/GetShardSnapshotResponse.java
index 08870248f2b8d..b17ccf5d56d1d 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/shard/GetShardSnapshotResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/shard/GetShardSnapshotResponse.java
@@ -34,7 +34,7 @@ public class GetShardSnapshotResponse extends ActionResponse {
     GetShardSnapshotResponse(StreamInput in) throws IOException {
         super(in);
         this.latestShardSnapshot = in.readOptionalWriteable(ShardSnapshotInfo::new);
-        this.repositoryFailures = in.readMap(StreamInput::readString, RepositoryException::new);
+        this.repositoryFailures = in.readMap(RepositoryException::new);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/admin/cluster/stats/SearchUsageStats.java b/server/src/main/java/org/elasticsearch/action/admin/cluster/stats/SearchUsageStats.java
index 639fb4b777155..fa60016e93f94 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/cluster/stats/SearchUsageStats.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/cluster/stats/SearchUsageStats.java
@@ -51,8 +51,8 @@ public SearchUsageStats(Map<String, Long> queries, Map<String, Long> sections, l
     }
 
     public SearchUsageStats(StreamInput in) throws IOException {
-        this.queries = in.readMap(StreamInput::readString, StreamInput::readLong);
-        this.sections = in.readMap(StreamInput::readString, StreamInput::readLong);
+        this.queries = in.readMap(StreamInput::readLong);
+        this.sections = in.readMap(StreamInput::readLong);
         this.totalSearchCount = in.readVLong();
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/alias/get/GetAliasesResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/alias/get/GetAliasesResponse.java
index a9c527a4fddf1..1ea6be9fea91b 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/alias/get/GetAliasesResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/alias/get/GetAliasesResponse.java
@@ -32,7 +32,7 @@ public GetAliasesResponse(Map<String, List<AliasMetadata>> aliases, Map<String,
     public GetAliasesResponse(StreamInput in) throws IOException {
         super(in);
         aliases = in.readImmutableOpenMap(StreamInput::readString, i -> i.readList(AliasMetadata::new));
-        dataStreamAliases = in.readMap(StreamInput::readString, in1 -> in1.readList(DataStreamAlias::new));
+        dataStreamAliases = in.readMap(in1 -> in1.readList(DataStreamAlias::new));
     }
 
     public Map<String, List<AliasMetadata>> getAliases() {
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/analyze/ReloadAnalyzersResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/analyze/ReloadAnalyzersResponse.java
index daff9c9b3b461..0e6149476659c 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/analyze/ReloadAnalyzersResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/analyze/ReloadAnalyzersResponse.java
@@ -45,7 +45,7 @@ public class ReloadAnalyzersResponse extends BroadcastResponse {
 
     public ReloadAnalyzersResponse(StreamInput in) throws IOException {
         super(in);
-        this.reloadDetails = in.readMap(StreamInput::readString, ReloadDetails::new);
+        this.reloadDetails = in.readMap(ReloadDetails::new);
     }
 
     public ReloadAnalyzersResponse(
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/AnalyzeIndexDiskUsageResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/AnalyzeIndexDiskUsageResponse.java
index 0fc1e9c01dc24..ce3c3f9897e4e 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/AnalyzeIndexDiskUsageResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/AnalyzeIndexDiskUsageResponse.java
@@ -34,7 +34,7 @@ public final class AnalyzeIndexDiskUsageResponse extends BroadcastResponse {
 
     AnalyzeIndexDiskUsageResponse(StreamInput in) throws IOException {
         super(in);
-        stats = in.readMap(StreamInput::readString, IndexDiskUsageStats::new);
+        stats = in.readMap(IndexDiskUsageStats::new);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/IndexDiskUsageStats.java b/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/IndexDiskUsageStats.java
index 7534f6653e470..6052543939819 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/IndexDiskUsageStats.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/diskusage/IndexDiskUsageStats.java
@@ -55,7 +55,7 @@ public IndexDiskUsageStats(long indexSizeInBytes) {
     }
 
     public IndexDiskUsageStats(StreamInput in) throws IOException {
-        this.fields = new HashMap<>(in.readMap(StreamInput::readString, PerFieldDiskUsage::new));
+        this.fields = new HashMap<>(in.readMap(PerFieldDiskUsage::new));
         this.indexSizeInBytes = in.readVLong();
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java
index fd6c815a7462b..03d2b05e09374 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetFieldMappingsResponse.java
@@ -51,7 +51,7 @@ public class GetFieldMappingsResponse extends ActionResponse implements ToXConte
 
     GetFieldMappingsResponse(StreamInput in) throws IOException {
         super(in);
-        mappings = in.readImmutableMap(StreamInput::readString, mapIn -> {
+        mappings = in.readImmutableMap(mapIn -> {
             if (mapIn.getTransportVersion().before(TransportVersion.V_8_0_0)) {
                 int typesSize = mapIn.readVInt();
                 assert typesSize == 1 || typesSize == 0 : "Expected 0 or 1 types but got " + typesSize;
@@ -60,10 +60,7 @@ public class GetFieldMappingsResponse extends ActionResponse implements ToXConte
                 }
                 mapIn.readString(); // type
             }
-            return mapIn.readImmutableMap(
-                StreamInput::readString,
-                inpt -> new FieldMappingMetadata(inpt.readString(), inpt.readBytesReference())
-            );
+            return mapIn.readImmutableMap(inpt -> new FieldMappingMetadata(inpt.readString(), inpt.readBytesReference()));
         });
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsResponse.java
index 22688f9f81a62..0ea5911a77e12 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/get/GetMappingsResponse.java
@@ -40,7 +40,7 @@ public GetMappingsResponse(Map<String, MappingMetadata> mappings) {
 
     GetMappingsResponse(StreamInput in) throws IOException {
         super(in);
-        mappings = in.readImmutableMap(StreamInput::readString, in.getTransportVersion().before(TransportVersion.V_8_0_0) ? i -> {
+        mappings = in.readImmutableMap(in.getTransportVersion().before(TransportVersion.V_8_0_0) ? i -> {
             int mappingCount = i.readVInt();
             assert mappingCount == 1 || mappingCount == 0 : "Expected 0 or 1 mappings but got " + mappingCount;
             if (mappingCount == 1) {
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/recovery/RecoveryResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/recovery/RecoveryResponse.java
index ea04ccf627633..a3b9432756b1f 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/recovery/RecoveryResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/recovery/RecoveryResponse.java
@@ -32,7 +32,7 @@ public class RecoveryResponse extends BaseBroadcastResponse implements ChunkedTo
 
     public RecoveryResponse(StreamInput in) throws IOException {
         super(in);
-        shardRecoveryStates = in.readMapOfLists(StreamInput::readString, RecoveryState::readRecoveryState);
+        shardRecoveryStates = in.readMapOfLists(RecoveryState::readRecoveryState);
     }
 
     /**
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/settings/get/GetSettingsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/settings/get/GetSettingsResponse.java
index fa95a93183c56..c3bb5dc71dc12 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/settings/get/GetSettingsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/settings/get/GetSettingsResponse.java
@@ -40,8 +40,8 @@ public GetSettingsResponse(Map<String, Settings> indexToSettings, Map<String, Se
 
     public GetSettingsResponse(StreamInput in) throws IOException {
         super(in);
-        indexToSettings = in.readImmutableMap(StreamInput::readString, Settings::readSettingsFromStream);
-        indexToDefaultSettings = in.readImmutableMap(StreamInput::readString, Settings::readSettingsFromStream);
+        indexToSettings = in.readImmutableMap(Settings::readSettingsFromStream);
+        indexToDefaultSettings = in.readImmutableMap(Settings::readSettingsFromStream);
     }
 
     /**
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesShardStoresResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesShardStoresResponse.java
index 6596a8de97677..2a981700118ed 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesShardStoresResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/shards/IndicesShardStoresResponse.java
@@ -245,10 +245,7 @@ public IndicesShardStoresResponse(Map<String, Map<Integer, List<StoreStatus>>> s
 
     public IndicesShardStoresResponse(StreamInput in) throws IOException {
         super(in);
-        storeStatuses = in.readImmutableMap(
-            StreamInput::readString,
-            i -> i.readImmutableMap(StreamInput::readInt, j -> j.readImmutableList(StoreStatus::new))
-        );
+        storeStatuses = in.readImmutableMap(i -> i.readImmutableMap(StreamInput::readInt, j -> j.readImmutableList(StoreStatus::new)));
         failures = in.readImmutableList(Failure::readFailure);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/stats/FieldUsageStatsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/stats/FieldUsageStatsResponse.java
index 9b2efa83746e2..3b5f919816708 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/stats/FieldUsageStatsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/stats/FieldUsageStatsResponse.java
@@ -35,7 +35,7 @@ public class FieldUsageStatsResponse extends ChunkedBroadcastResponse {
 
     FieldUsageStatsResponse(StreamInput in) throws IOException {
         super(in);
-        stats = in.readMap(StreamInput::readString, i -> i.readList(FieldUsageShardResponse::new));
+        stats = in.readMap(i -> i.readList(FieldUsageShardResponse::new));
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/stats/IndicesStatsResponse.java b/server/src/main/java/org/elasticsearch/action/admin/indices/stats/IndicesStatsResponse.java
index 76566e03bcdf1..399a1908061e1 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/stats/IndicesStatsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/stats/IndicesStatsResponse.java
@@ -52,8 +52,8 @@ public class IndicesStatsResponse extends ChunkedBroadcastResponse {
         super(in);
         shards = in.readArray(ShardStats::new, ShardStats[]::new);
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_1_0)) {
-            indexHealthMap = in.readMap(StreamInput::readString, ClusterHealthStatus::readFrom);
-            indexStateMap = in.readMap(StreamInput::readString, IndexMetadata.State::readFrom);
+            indexHealthMap = in.readMap(ClusterHealthStatus::readFrom);
+            indexStateMap = in.readMap(IndexMetadata.State::readFrom);
         } else {
             indexHealthMap = Map.of();
             indexStateMap = Map.of();
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComponentTemplateAction.java b/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComponentTemplateAction.java
index 20d6f7f339765..b1a55fcea58e6 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComponentTemplateAction.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComponentTemplateAction.java
@@ -120,7 +120,7 @@ public static class Response extends ActionResponse implements ToXContentObject
 
         public Response(StreamInput in) throws IOException {
             super(in);
-            componentTemplates = in.readMap(StreamInput::readString, ComponentTemplate::new);
+            componentTemplates = in.readMap(ComponentTemplate::new);
             if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_500_007)) {
                 rolloverConfiguration = in.readOptionalWriteable(RolloverConfiguration::new);
             } else {
diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComposableIndexTemplateAction.java b/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComposableIndexTemplateAction.java
index d35eddb755fdc..481ff97781398 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComposableIndexTemplateAction.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/template/get/GetComposableIndexTemplateAction.java
@@ -122,7 +122,7 @@ public static class Response extends ActionResponse implements ToXContentObject
 
         public Response(StreamInput in) throws IOException {
             super(in);
-            indexTemplates = in.readMap(StreamInput::readString, ComposableIndexTemplate::new);
+            indexTemplates = in.readMap(ComposableIndexTemplate::new);
             if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_500_007)) {
                 rolloverConfiguration = in.readOptionalWriteable(RolloverConfiguration::new);
             } else {
diff --git a/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilities.java b/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilities.java
index daa9ee30bf9aa..c3363e5c812cc 100644
--- a/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilities.java
+++ b/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilities.java
@@ -244,7 +244,7 @@ public FieldCapabilities(
             this.nonDimensionIndices = null;
             this.metricConflictsIndices = null;
         }
-        meta = in.readMap(StreamInput::readString, i -> i.readSet(StreamInput::readString));
+        meta = in.readMap(i -> i.readSet(StreamInput::readString));
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesIndexResponse.java b/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesIndexResponse.java
index 57183c49cdef2..8c2ea2679ac4b 100644
--- a/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesIndexResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesIndexResponse.java
@@ -47,7 +47,7 @@ final class FieldCapabilitiesIndexResponse implements Writeable {
 
     FieldCapabilitiesIndexResponse(StreamInput in) throws IOException {
         this.indexName = in.readString();
-        this.responseMap = in.readMap(StreamInput::readString, IndexFieldCapabilities::new);
+        this.responseMap = in.readMap(IndexFieldCapabilities::new);
         this.canMatch = in.readBoolean();
         this.originVersion = in.getTransportVersion();
         if (in.getTransportVersion().onOrAfter(MAPPING_HASH_VERSION)) {
@@ -71,7 +71,7 @@ private record GroupByMappingHash(List<String> indices, String indexMappingHash,
         implements
             Writeable {
         GroupByMappingHash(StreamInput in) throws IOException {
-            this(in.readStringList(), in.readString(), in.readMap(StreamInput::readString, IndexFieldCapabilities::new));
+            this(in.readStringList(), in.readString(), in.readMap(IndexFieldCapabilities::new));
         }
 
         @Override
diff --git a/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesResponse.java b/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesResponse.java
index 44ab201eb3681..ea6fb326a2b1e 100644
--- a/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/fieldcaps/FieldCapabilitiesResponse.java
@@ -76,7 +76,7 @@ private FieldCapabilitiesResponse(
     public FieldCapabilitiesResponse(StreamInput in) throws IOException {
         super(in);
         indices = in.readStringArray();
-        this.responseMap = in.readMap(StreamInput::readString, FieldCapabilitiesResponse::readField);
+        this.responseMap = in.readMap(FieldCapabilitiesResponse::readField);
         this.indexResponses = FieldCapabilitiesIndexResponse.readList(in);
         this.failures = in.readList(FieldCapabilitiesFailure::new);
     }
@@ -136,7 +136,7 @@ public boolean isMetadataField(String field) {
     }
 
     private static Map<String, FieldCapabilities> readField(StreamInput in) throws IOException {
-        return in.readMap(StreamInput::readString, FieldCapabilities::new);
+        return in.readMap(FieldCapabilities::new);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java b/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java
index 9b3b7cd08c6cc..5b9ac325d1cf0 100644
--- a/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java
+++ b/server/src/main/java/org/elasticsearch/action/fieldcaps/IndexFieldCapabilities.java
@@ -75,7 +75,7 @@ public class IndexFieldCapabilities implements Writeable {
             this.isDimension = false;
             this.metricType = null;
         }
-        this.meta = in.readMap(StreamInput::readString, StreamInput::readString);
+        this.meta = in.readMap(StreamInput::readString);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java b/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
index 9ac18519e30a2..d179ffdd242b4 100644
--- a/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/index/IndexRequest.java
@@ -159,7 +159,7 @@ public IndexRequest(@Nullable ShardId shardId, StreamInput in) throws IOExceptio
             requireAlias = false;
         }
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_13_0)) {
-            dynamicTemplates = in.readMap(StreamInput::readString, StreamInput::readString);
+            dynamicTemplates = in.readMap(StreamInput::readString);
         }
     }
 
diff --git a/server/src/main/java/org/elasticsearch/action/search/SearchContextId.java b/server/src/main/java/org/elasticsearch/action/search/SearchContextId.java
index 7e809a11ea1d0..4fb90cb871d21 100644
--- a/server/src/main/java/org/elasticsearch/action/search/SearchContextId.java
+++ b/server/src/main/java/org/elasticsearch/action/search/SearchContextId.java
@@ -93,7 +93,7 @@ public static SearchContextId decode(NamedWriteableRegistry namedWriteableRegist
             final TransportVersion version = TransportVersion.readVersion(in);
             in.setTransportVersion(version);
             final Map<ShardId, SearchContextIdForNode> shards = in.readMap(ShardId::new, SearchContextIdForNode::new);
-            final Map<String, AliasFilter> aliasFilters = in.readMap(StreamInput::readString, AliasFilter::readFrom);
+            final Map<String, AliasFilter> aliasFilters = in.readMap(AliasFilter::readFrom);
             if (in.available() > 0) {
                 throw new IllegalArgumentException("Not all bytes were read");
             }
diff --git a/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java b/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java
index 36c41aa1ed334..aff813b6a5373 100644
--- a/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/search/SearchRequest.java
@@ -268,7 +268,7 @@ public SearchRequest(StreamInput in) throws IOException {
             minCompatibleShardNode = null;
         }
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_16_0)) {
-            waitForCheckpoints = in.readMap(StreamInput::readString, StreamInput::readLongArray);
+            waitForCheckpoints = in.readMap(StreamInput::readLongArray);
             waitForCheckpointsTimeout = in.readTimeValue();
         }
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_4_0)) {
diff --git a/server/src/main/java/org/elasticsearch/action/search/SearchShardsResponse.java b/server/src/main/java/org/elasticsearch/action/search/SearchShardsResponse.java
index e70e0677e0e5f..5f34d40e2efb3 100644
--- a/server/src/main/java/org/elasticsearch/action/search/SearchShardsResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/search/SearchShardsResponse.java
@@ -49,7 +49,7 @@ public SearchShardsResponse(StreamInput in) throws IOException {
         super(in);
         this.groups = in.readList(SearchShardsGroup::new);
         this.nodes = in.readList(DiscoveryNode::new);
-        this.aliasFilters = in.readMap(StreamInput::readString, AliasFilter::readFrom);
+        this.aliasFilters = in.readMap(AliasFilter::readFrom);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsFields.java b/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsFields.java
index 5e2d3c22a79fa..805bd055c97d7 100644
--- a/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsFields.java
+++ b/server/src/main/java/org/elasticsearch/action/termvectors/TermVectorsFields.java
@@ -131,7 +131,7 @@ public TermVectorsFields(BytesReference headerRef, BytesReference termVectors) t
             hasTermStatistic = header.readBoolean();
             hasFieldStatistic = header.readBoolean();
             hasScores = header.readBoolean();
-            fieldMap = header.readMap(StreamInput::readString, StreamInput::readVLong);
+            fieldMap = header.readMap(StreamInput::readVLong);
         }
         // reference to the term vector data
         this.termVectors = termVectors;
diff --git a/server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java b/server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java
index 6b9e0f85f145b..7fc85f64fee8e 100644
--- a/server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java
+++ b/server/src/main/java/org/elasticsearch/cluster/ClusterInfo.java
@@ -84,9 +84,9 @@ public ClusterInfo(
     }
 
     public ClusterInfo(StreamInput in) throws IOException {
-        this.leastAvailableSpaceUsage = in.readImmutableMap(StreamInput::readString, DiskUsage::new);
-        this.mostAvailableSpaceUsage = in.readImmutableMap(StreamInput::readString, DiskUsage::new);
-        this.shardSizes = in.readImmutableMap(StreamInput::readString, StreamInput::readLong);
+        this.leastAvailableSpaceUsage = in.readImmutableMap(DiskUsage::new);
+        this.mostAvailableSpaceUsage = in.readImmutableMap(DiskUsage::new);
+        this.shardSizes = in.readImmutableMap(StreamInput::readLong);
         this.shardDataSetSizes = in.getTransportVersion().onOrAfter(DATA_SET_SIZE_SIZE_VERSION)
             ? in.readImmutableMap(ShardId::new, StreamInput::readLong)
             : Map.of();
diff --git a/server/src/main/java/org/elasticsearch/cluster/ClusterState.java b/server/src/main/java/org/elasticsearch/cluster/ClusterState.java
index e466aa0d69a23..c5a72f97ea940 100644
--- a/server/src/main/java/org/elasticsearch/cluster/ClusterState.java
+++ b/server/src/main/java/org/elasticsearch/cluster/ClusterState.java
@@ -908,7 +908,7 @@ public static ClusterState readFrom(StreamInput in, DiscoveryNode localNode) thr
         builder.routingTable = RoutingTable.readFrom(in);
         builder.nodes = DiscoveryNodes.readFrom(in, localNode);
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_8_0)) {
-            builder.transportVersions(in.readMap(StreamInput::readString, TransportVersion::readVersion));
+            builder.transportVersions(in.readMap(TransportVersion::readVersion));
         } else {
             // this clusterstate is from a pre-8.8.0 node
             // infer the versions from discoverynodes for now
diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/ClusterFormationFailureHelper.java b/server/src/main/java/org/elasticsearch/cluster/coordination/ClusterFormationFailureHelper.java
index be82c8955a183..50bc9479ee540 100644
--- a/server/src/main/java/org/elasticsearch/cluster/coordination/ClusterFormationFailureHelper.java
+++ b/server/src/main/java/org/elasticsearch/cluster/coordination/ClusterFormationFailureHelper.java
@@ -206,7 +206,7 @@ public ClusterFormationState(StreamInput in) throws IOException {
             this(
                 in.readStringList(),
                 new DiscoveryNode(in),
-                in.readMap(StreamInput::readString, DiscoveryNode::new),
+                in.readMap(DiscoveryNode::new),
                 in.readLong(),
                 in.readLong(),
                 new VotingConfiguration(in),
diff --git a/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java b/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java
index 8d7a706ed53ed..ca4fb9f07fc75 100644
--- a/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java
+++ b/server/src/main/java/org/elasticsearch/cluster/coordination/CoordinationDiagnosticsService.java
@@ -1291,7 +1291,7 @@ private static List<DiscoveryNode> readRecentMasters(StreamInput in) throws IOEx
 
         private static Map<String, String> readClusterFormationStates(StreamInput in) throws IOException {
             if (in.readBoolean()) {
-                return in.readMap(StreamInput::readString, StreamInput::readString);
+                return in.readMap(StreamInput::readString);
             } else {
                 return Map.of();
             }
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/ComponentTemplateMetadata.java b/server/src/main/java/org/elasticsearch/cluster/metadata/ComponentTemplateMetadata.java
index 26548f7b824ca..67582a5e27559 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/ComponentTemplateMetadata.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/ComponentTemplateMetadata.java
@@ -59,7 +59,7 @@ public ComponentTemplateMetadata(Map<String, ComponentTemplate> componentTemplat
     }
 
     public ComponentTemplateMetadata(StreamInput in) throws IOException {
-        this.componentTemplates = in.readMap(StreamInput::readString, ComponentTemplate::new);
+        this.componentTemplates = in.readMap(ComponentTemplate::new);
     }
 
     public Map<String, ComponentTemplate> componentTemplates() {
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/ComposableIndexTemplateMetadata.java b/server/src/main/java/org/elasticsearch/cluster/metadata/ComposableIndexTemplateMetadata.java
index 53c73c7906b94..6da5bf26e427f 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/ComposableIndexTemplateMetadata.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/ComposableIndexTemplateMetadata.java
@@ -60,7 +60,7 @@ public ComposableIndexTemplateMetadata(Map<String, ComposableIndexTemplate> temp
     }
 
     public ComposableIndexTemplateMetadata(StreamInput in) throws IOException {
-        this.indexTemplates = in.readMap(StreamInput::readString, ComposableIndexTemplate::new);
+        this.indexTemplates = in.readMap(ComposableIndexTemplate::new);
     }
 
     public static ComposableIndexTemplateMetadata fromXContent(XContentParser parser) throws IOException {
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamAlias.java b/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamAlias.java
index 7efba02dfe341..be8613f5790ba 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamAlias.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamAlias.java
@@ -168,7 +168,7 @@ public DataStreamAlias(StreamInput in) throws IOException {
         this.dataStreams = in.readStringList();
         this.writeDataStream = in.readOptionalString();
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_7_0)) {
-            this.dataStreamToFilterMap = in.readMap(StreamInput::readString, CompressedXContent::readCompressedString);
+            this.dataStreamToFilterMap = in.readMap(CompressedXContent::readCompressedString);
         } else {
             this.dataStreamToFilterMap = new HashMap<>();
             CompressedXContent filter = in.readBoolean() ? CompressedXContent.readCompressedString(in) : null;
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/DiffableStringMap.java b/server/src/main/java/org/elasticsearch/cluster/metadata/DiffableStringMap.java
index 1859616865dda..a26bf8189117e 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/DiffableStringMap.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/DiffableStringMap.java
@@ -89,7 +89,7 @@ public Diff<DiffableStringMap> diff(DiffableStringMap previousState) {
 
     public static Diff<DiffableStringMap> readDiffFrom(StreamInput in) throws IOException {
         final List<String> deletes = in.readStringList();
-        final Map<String, String> upserts = in.readMap(StreamInput::readString, StreamInput::readString);
+        final Map<String, String> upserts = in.readMap(StreamInput::readString);
         return getDiff(deletes, upserts);
     }
 
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/NodesShutdownMetadata.java b/server/src/main/java/org/elasticsearch/cluster/metadata/NodesShutdownMetadata.java
index 5222eb1605591..a5207adb20b01 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/NodesShutdownMetadata.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/NodesShutdownMetadata.java
@@ -74,7 +74,7 @@ public NodesShutdownMetadata(Map<String, SingleNodeShutdownMetadata> nodes) {
     }
 
     public NodesShutdownMetadata(StreamInput in) throws IOException {
-        this(in.readImmutableMap(StreamInput::readString, SingleNodeShutdownMetadata::new));
+        this(in.readImmutableMap(SingleNodeShutdownMetadata::new));
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/cluster/metadata/Template.java b/server/src/main/java/org/elasticsearch/cluster/metadata/Template.java
index 6b4e003ce7f49..0b6ca729f98cc 100644
--- a/server/src/main/java/org/elasticsearch/cluster/metadata/Template.java
+++ b/server/src/main/java/org/elasticsearch/cluster/metadata/Template.java
@@ -145,7 +145,7 @@ public Template(StreamInput in) throws IOException {
             this.mappings = null;
         }
         if (in.readBoolean()) {
-            this.aliases = in.readMap(StreamInput::readString, AliasMetadata::new);
+            this.aliases = in.readMap(AliasMetadata::new);
         } else {
             this.aliases = null;
         }
diff --git a/server/src/main/java/org/elasticsearch/cluster/routing/allocation/allocator/ClusterBalanceStats.java b/server/src/main/java/org/elasticsearch/cluster/routing/allocation/allocator/ClusterBalanceStats.java
index 8076d48775ae5..56a42cff10fbb 100644
--- a/server/src/main/java/org/elasticsearch/cluster/routing/allocation/allocator/ClusterBalanceStats.java
+++ b/server/src/main/java/org/elasticsearch/cluster/routing/allocation/allocator/ClusterBalanceStats.java
@@ -60,10 +60,7 @@ public static ClusterBalanceStats createFrom(
     }
 
     public static ClusterBalanceStats readFrom(StreamInput in) throws IOException {
-        return new ClusterBalanceStats(
-            in.readImmutableMap(StreamInput::readString, TierBalanceStats::readFrom),
-            in.readImmutableMap(StreamInput::readString, NodeBalanceStats::readFrom)
-        );
+        return new ClusterBalanceStats(in.readImmutableMap(TierBalanceStats::readFrom), in.readImmutableMap(NodeBalanceStats::readFrom));
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/common/FieldMemoryStats.java b/server/src/main/java/org/elasticsearch/common/FieldMemoryStats.java
index 6f0f69e9e6504..1785ca96c4ab3 100644
--- a/server/src/main/java/org/elasticsearch/common/FieldMemoryStats.java
+++ b/server/src/main/java/org/elasticsearch/common/FieldMemoryStats.java
@@ -39,7 +39,7 @@ public FieldMemoryStats(Map<String, Long> stats) {
      * Creates a new FieldMemoryStats instance from a stream
      */
     public FieldMemoryStats(StreamInput input) throws IOException {
-        stats = input.readMap(StreamInput::readString, StreamInput::readVLong);
+        stats = input.readMap(StreamInput::readVLong);
     }
 
     /**
diff --git a/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java b/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java
index 9ea8bc127dd57..6b43e59177cde 100644
--- a/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java
+++ b/server/src/main/java/org/elasticsearch/common/io/stream/StreamInput.java
@@ -618,6 +618,13 @@ public byte[] readOptionalByteArray() throws IOException {
         return null;
     }
 
+    /**
+     * Same as {@link #readMap(Writeable.Reader, Writeable.Reader)} but always reading string keys.
+     */
+    public <V> Map<String, V> readMap(Writeable.Reader<V> valueReader) throws IOException {
+        return readMap(StreamInput::readString, valueReader, Maps::newHashMapWithExpectedSize);
+    }
+
     /**
      * If the returned map contains any entries it will be mutable. If it is empty it might be immutable.
      */
@@ -645,28 +652,18 @@ private <K, V> Map<K, V> readMap(Writeable.Reader<K> keyReader, Writeable.Reader
     }
 
     /**
-     * Read a {@link Map} of {@code K}-type keys to {@code V}-type {@link List}s.
+     * Read a {@link Map} of string keys to {@code V}-type {@link List}s.
      * <pre><code>
-     * Map&lt;String, List&lt;String&gt;&gt; map = in.readMapOfLists(StreamInput::readString, StreamInput::readString);
+     * Map&lt;String, List&lt;String&gt;&gt; map = in.readMapOfLists(StreamInput::readString);
      * </code></pre>
      * If the map or a list in it contains any elements it will be mutable, otherwise either the empty map or empty lists it contains
      * might be immutable.
      *
-     * @param keyReader The key reader
      * @param valueReader The value reader
      * @return Never {@code null}.
      */
-    public <K, V> Map<K, List<V>> readMapOfLists(final Writeable.Reader<K> keyReader, final Writeable.Reader<V> valueReader)
-        throws IOException {
-        final int size = readArraySize();
-        if (size == 0) {
-            return Collections.emptyMap();
-        }
-        final Map<K, List<V>> map = Maps.newMapWithExpectedSize(size);
-        for (int i = 0; i < size; ++i) {
-            map.put(keyReader.read(this), readList(valueReader));
-        }
-        return map;
+    public <V> Map<String, List<V>> readMapOfLists(final Writeable.Reader<V> valueReader) throws IOException {
+        return readMap(i -> i.readList(valueReader));
     }
 
     /**
@@ -698,6 +695,13 @@ public Map<String, Object> readMap() throws IOException {
         return (Map<String, Object>) readGenericValue();
     }
 
+    /**
+     * Same as {@link #readMap(Writeable.Reader, Writeable.Reader)} but always reading string keys.
+     */
+    public <V> Map<String, V> readImmutableMap(Writeable.Reader<V> valueReader) throws IOException {
+        return readImmutableMap(StreamInput::readString, valueReader);
+    }
+
     /**
      * Read a {@link Map} using the given key and value readers. The return Map is immutable.
      *
@@ -762,7 +766,7 @@ public Object readGenericValue() throws IOException {
                 : readOrderedMap(StreamInput::readString, StreamInput::readGenericValue);
             case 10 -> getTransportVersion().onOrAfter(TransportVersion.V_8_7_0)
                 ? readMap(StreamInput::readGenericValue, StreamInput::readGenericValue)
-                : readMap(StreamInput::readString, StreamInput::readGenericValue);
+                : readMap(StreamInput::readGenericValue);
             case 11 -> readByte();
             case 12 -> readDate();
             case 13 ->
diff --git a/server/src/main/java/org/elasticsearch/common/settings/KeyStoreWrapper.java b/server/src/main/java/org/elasticsearch/common/settings/KeyStoreWrapper.java
index 20cc210dd78f4..4a00cc1250461 100644
--- a/server/src/main/java/org/elasticsearch/common/settings/KeyStoreWrapper.java
+++ b/server/src/main/java/org/elasticsearch/common/settings/KeyStoreWrapper.java
@@ -179,7 +179,7 @@ public KeyStoreWrapper(StreamInput input) throws IOException {
         formatVersion = input.readInt();
         hasPassword = input.readBoolean();
         dataBytes = input.readOptionalByteArray();
-        entries.set(input.readMap(StreamInput::readString, Entry::new));
+        entries.set(input.readMap(Entry::new));
         closed = input.readBoolean();
     }
 
diff --git a/server/src/main/java/org/elasticsearch/common/settings/LocallyMountedSecrets.java b/server/src/main/java/org/elasticsearch/common/settings/LocallyMountedSecrets.java
index 05801af60027a..ddbf5ec2bbc96 100644
--- a/server/src/main/java/org/elasticsearch/common/settings/LocallyMountedSecrets.java
+++ b/server/src/main/java/org/elasticsearch/common/settings/LocallyMountedSecrets.java
@@ -252,7 +252,7 @@ record LocalFileSecrets(Map<String, byte[]> entries, ReservedStateVersion metada
          */
         public static LocalFileSecrets readFrom(StreamInput in) throws IOException {
             assert in.getTransportVersion() == TransportVersion.current();
-            return new LocalFileSecrets(in.readMap(StreamInput::readString, StreamInput::readByteArray), ReservedStateVersion.readFrom(in));
+            return new LocalFileSecrets(in.readMap(StreamInput::readByteArray), ReservedStateVersion.readFrom(in));
         }
 
         /**
diff --git a/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java b/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java
index 7678d3f7d10ab..551af04e1956f 100644
--- a/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java
+++ b/server/src/main/java/org/elasticsearch/common/util/concurrent/ThreadContext.java
@@ -463,8 +463,8 @@ public void setHeaders(Tuple<Map<String, String>, Map<String, Set<String>>> head
     }
 
     public static Tuple<Map<String, String>, Map<String, Set<String>>> readHeadersFromStream(StreamInput in) throws IOException {
-        final Map<String, String> requestHeaders = in.readMap(StreamInput::readString, StreamInput::readString);
-        final Map<String, Set<String>> responseHeaders = in.readMap(StreamInput::readString, input -> {
+        final Map<String, String> requestHeaders = in.readMap(StreamInput::readString);
+        final Map<String, Set<String>> responseHeaders = in.readMap(input -> {
             final int size = input.readVInt();
             if (size == 0) {
                 return Collections.emptySet();
diff --git a/server/src/main/java/org/elasticsearch/health/node/HealthInfo.java b/server/src/main/java/org/elasticsearch/health/node/HealthInfo.java
index d87609a904157..f83d5916a792e 100644
--- a/server/src/main/java/org/elasticsearch/health/node/HealthInfo.java
+++ b/server/src/main/java/org/elasticsearch/health/node/HealthInfo.java
@@ -23,7 +23,7 @@ public record HealthInfo(Map<String, DiskHealthInfo> diskInfoByNode) implements
     public static final HealthInfo EMPTY_HEALTH_INFO = new HealthInfo(Map.of());
 
     public HealthInfo(StreamInput input) throws IOException {
-        this(input.readMap(StreamInput::readString, DiskHealthInfo::new));
+        this(input.readMap(DiskHealthInfo::new));
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/index/engine/CommitStats.java b/server/src/main/java/org/elasticsearch/index/engine/CommitStats.java
index d93c71be1cb15..1a44f1f46c33e 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/CommitStats.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/CommitStats.java
@@ -38,7 +38,7 @@ public CommitStats(SegmentInfos segmentInfos) {
     }
 
     CommitStats(StreamInput in) throws IOException {
-        userData = in.readImmutableMap(StreamInput::readString, StreamInput::readString);
+        userData = in.readImmutableMap(StreamInput::readString);
         generation = in.readLong();
         id = in.readOptionalString();
         numDocs = in.readInt();
diff --git a/server/src/main/java/org/elasticsearch/index/engine/Segment.java b/server/src/main/java/org/elasticsearch/index/engine/Segment.java
index 88dbe7d454a3d..acfb1ac8920a1 100644
--- a/server/src/main/java/org/elasticsearch/index/engine/Segment.java
+++ b/server/src/main/java/org/elasticsearch/index/engine/Segment.java
@@ -60,7 +60,7 @@ public Segment(StreamInput in) throws IOException {
         }
         segmentSort = readSegmentSort(in);
         if (in.readBoolean()) {
-            attributes = in.readMap(StreamInput::readString, StreamInput::readString);
+            attributes = in.readMap(StreamInput::readString);
         } else {
             attributes = null;
         }
diff --git a/server/src/main/java/org/elasticsearch/index/fielddata/FieldDataStats.java b/server/src/main/java/org/elasticsearch/index/fielddata/FieldDataStats.java
index 5b21bcbfd599f..07b92f97aa8ae 100644
--- a/server/src/main/java/org/elasticsearch/index/fielddata/FieldDataStats.java
+++ b/server/src/main/java/org/elasticsearch/index/fielddata/FieldDataStats.java
@@ -52,7 +52,6 @@ public FieldDataStats(StreamInput in) throws IOException {
             Map<String, GlobalOrdinalsStats.GlobalOrdinalFieldStats> fieldGlobalOrdinalsStats = null;
             if (in.readBoolean()) {
                 fieldGlobalOrdinalsStats = in.readMap(
-                    StreamInput::readString,
                     in1 -> new GlobalOrdinalsStats.GlobalOrdinalFieldStats(in1.readVLong(), in1.readVLong())
                 );
             }
diff --git a/server/src/main/java/org/elasticsearch/index/search/stats/FieldUsageStats.java b/server/src/main/java/org/elasticsearch/index/search/stats/FieldUsageStats.java
index 93d047a87c4da..1a0be7523ba08 100644
--- a/server/src/main/java/org/elasticsearch/index/search/stats/FieldUsageStats.java
+++ b/server/src/main/java/org/elasticsearch/index/search/stats/FieldUsageStats.java
@@ -52,7 +52,7 @@ public FieldUsageStats(Map<String, PerFieldUsageStats> stats) {
     }
 
     public FieldUsageStats(StreamInput in) throws IOException {
-        stats = in.readMap(StreamInput::readString, PerFieldUsageStats::new);
+        stats = in.readMap(PerFieldUsageStats::new);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/index/search/stats/SearchStats.java b/server/src/main/java/org/elasticsearch/index/search/stats/SearchStats.java
index ca0932f2107da..22fdf8ecd2bc3 100644
--- a/server/src/main/java/org/elasticsearch/index/search/stats/SearchStats.java
+++ b/server/src/main/java/org/elasticsearch/index/search/stats/SearchStats.java
@@ -297,7 +297,7 @@ public SearchStats(StreamInput in) throws IOException {
         totalStats = Stats.readStats(in);
         openContexts = in.readVLong();
         if (in.readBoolean()) {
-            groupStats = in.readMap(StreamInput::readString, Stats::readStats);
+            groupStats = in.readMap(Stats::readStats);
         }
     }
 
diff --git a/server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java b/server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java
index 333a1b177b965..1dd23f0b0a15e 100644
--- a/server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java
+++ b/server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java
@@ -1583,7 +1583,7 @@ public PrimaryContext(long clusterStateVersion, Map<String, CheckpointState> che
 
         public PrimaryContext(StreamInput in) throws IOException {
             clusterStateVersion = in.readVLong();
-            checkpoints = in.readMap(StreamInput::readString, CheckpointState::new);
+            checkpoints = in.readMap(CheckpointState::new);
             routingTable = IndexShardRoutingTable.Builder.readFrom(in).build();
         }
 
diff --git a/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java b/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java
index f416178a6b10d..22f3da92eebaf 100644
--- a/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java
+++ b/server/src/main/java/org/elasticsearch/index/shard/IndexingStats.java
@@ -270,7 +270,7 @@ public IndexingStats(StreamInput in) throws IOException {
         totalStats = new Stats(in);
         if (in.getTransportVersion().before(TransportVersion.V_8_0_0)) {
             if (in.readBoolean()) {
-                Map<String, Stats> typeStats = in.readMap(StreamInput::readString, Stats::new);
+                Map<String, Stats> typeStats = in.readMap(Stats::new);
                 assert typeStats.size() == 1;
                 assert typeStats.containsKey(MapperService.SINGLE_MAPPING_NAME);
             }
diff --git a/server/src/main/java/org/elasticsearch/index/store/Store.java b/server/src/main/java/org/elasticsearch/index/store/Store.java
index b70683ee1f775..74e1bc88a3b82 100644
--- a/server/src/main/java/org/elasticsearch/index/store/Store.java
+++ b/server/src/main/java/org/elasticsearch/index/store/Store.java
@@ -860,7 +860,7 @@ static MetadataSnapshot loadFromIndexCommit(IndexCommit commit, Directory direct
 
         public static MetadataSnapshot readFrom(StreamInput in) throws IOException {
             final Map<String, StoreFileMetadata> metadata = in.readMapValues(StoreFileMetadata::new, StoreFileMetadata::name);
-            final var commitUserData = in.readMap(StreamInput::readString, StreamInput::readString);
+            final var commitUserData = in.readMap(StreamInput::readString);
             final var numDocs = in.readLong();
 
             if (metadata.size() == 0 && commitUserData.size() == 0 && numDocs == 0) {
diff --git a/server/src/main/java/org/elasticsearch/monitor/jvm/JvmInfo.java b/server/src/main/java/org/elasticsearch/monitor/jvm/JvmInfo.java
index f928f83531aa0..d4a15bea858e3 100644
--- a/server/src/main/java/org/elasticsearch/monitor/jvm/JvmInfo.java
+++ b/server/src/main/java/org/elasticsearch/monitor/jvm/JvmInfo.java
@@ -280,7 +280,7 @@ public JvmInfo(StreamInput in) throws IOException {
         }
         bootClassPath = in.readString();
         classPath = in.readString();
-        systemProperties = in.readMap(StreamInput::readString, StreamInput::readString);
+        systemProperties = in.readMap(StreamInput::readString);
         mem = new Mem(in);
         gcCollectors = in.readStringArray();
         memoryPools = in.readStringArray();
diff --git a/server/src/main/java/org/elasticsearch/node/AdaptiveSelectionStats.java b/server/src/main/java/org/elasticsearch/node/AdaptiveSelectionStats.java
index 833cec370ff6f..0f54d7ce43b61 100644
--- a/server/src/main/java/org/elasticsearch/node/AdaptiveSelectionStats.java
+++ b/server/src/main/java/org/elasticsearch/node/AdaptiveSelectionStats.java
@@ -42,8 +42,8 @@ public AdaptiveSelectionStats(
     }
 
     public AdaptiveSelectionStats(StreamInput in) throws IOException {
-        this.clientOutgoingConnections = in.readMap(StreamInput::readString, StreamInput::readLong);
-        this.nodeComputedStats = in.readMap(StreamInput::readString, ResponseCollectorService.ComputedNodeStats::new);
+        this.clientOutgoingConnections = in.readMap(StreamInput::readLong);
+        this.nodeComputedStats = in.readMap(ResponseCollectorService.ComputedNodeStats::new);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/persistent/PersistentTasksCustomMetadata.java b/server/src/main/java/org/elasticsearch/persistent/PersistentTasksCustomMetadata.java
index 9a3adb06ae296..1ce3ab6633faf 100644
--- a/server/src/main/java/org/elasticsearch/persistent/PersistentTasksCustomMetadata.java
+++ b/server/src/main/java/org/elasticsearch/persistent/PersistentTasksCustomMetadata.java
@@ -532,7 +532,7 @@ public String getWriteableName() {
 
     public PersistentTasksCustomMetadata(StreamInput in) throws IOException {
         lastAllocationId = in.readLong();
-        tasks = in.readMap(StreamInput::readString, PersistentTask::new);
+        tasks = in.readMap(PersistentTask::new);
     }
 
     @Override
diff --git a/server/src/main/java/org/elasticsearch/repositories/RepositoriesStats.java b/server/src/main/java/org/elasticsearch/repositories/RepositoriesStats.java
index 5e4f3fd39cad9..6a13053ec9279 100644
--- a/server/src/main/java/org/elasticsearch/repositories/RepositoriesStats.java
+++ b/server/src/main/java/org/elasticsearch/repositories/RepositoriesStats.java
@@ -29,7 +29,7 @@ public class RepositoriesStats implements Writeable, ToXContentFragment {
 
     public RepositoriesStats(StreamInput in) throws IOException {
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_500_011)) {
-            repositoryThrottlingStats = in.readMap(StreamInput::readString, ThrottlingStats::new);
+            repositoryThrottlingStats = in.readMap(ThrottlingStats::new);
         } else {
             repositoryThrottlingStats = new HashMap<>();
         }
diff --git a/server/src/main/java/org/elasticsearch/repositories/RepositoryInfo.java b/server/src/main/java/org/elasticsearch/repositories/RepositoryInfo.java
index 040d02acfcc8a..fe3251a10d7fb 100644
--- a/server/src/main/java/org/elasticsearch/repositories/RepositoryInfo.java
+++ b/server/src/main/java/org/elasticsearch/repositories/RepositoryInfo.java
@@ -56,7 +56,7 @@ public RepositoryInfo(StreamInput in) throws IOException {
         this.ephemeralId = in.readString();
         this.name = in.readString();
         this.type = in.readString();
-        this.location = in.readMap(StreamInput::readString, StreamInput::readString);
+        this.location = in.readMap(StreamInput::readString);
         this.startedAt = in.readLong();
         this.stoppedAt = in.readOptionalLong();
     }
diff --git a/server/src/main/java/org/elasticsearch/repositories/RepositoryStats.java b/server/src/main/java/org/elasticsearch/repositories/RepositoryStats.java
index aee9d7c7cced2..b991b3954edfc 100644
--- a/server/src/main/java/org/elasticsearch/repositories/RepositoryStats.java
+++ b/server/src/main/java/org/elasticsearch/repositories/RepositoryStats.java
@@ -29,7 +29,7 @@ public RepositoryStats(Map<String, Long> requestCounts) {
     }
 
     public RepositoryStats(StreamInput in) throws IOException {
-        this.requestCounts = in.readMap(StreamInput::readString, StreamInput::readLong);
+        this.requestCounts = in.readMap(StreamInput::readLong);
     }
 
     public RepositoryStats merge(RepositoryStats otherStats) {
diff --git a/server/src/main/java/org/elasticsearch/script/ScriptLanguagesInfo.java b/server/src/main/java/org/elasticsearch/script/ScriptLanguagesInfo.java
index 4e26fed09c94e..8993188c36c24 100644
--- a/server/src/main/java/org/elasticsearch/script/ScriptLanguagesInfo.java
+++ b/server/src/main/java/org/elasticsearch/script/ScriptLanguagesInfo.java
@@ -83,7 +83,7 @@ public ScriptLanguagesInfo(Set<String> typesAllowed, Map<String, Set<String>> la
 
     public ScriptLanguagesInfo(StreamInput in) throws IOException {
         typesAllowed = in.readImmutableSet(StreamInput::readString);
-        languageContexts = in.readImmutableMap(StreamInput::readString, sin -> sin.readImmutableSet(StreamInput::readString));
+        languageContexts = in.readImmutableMap(sin -> sin.readImmutableSet(StreamInput::readString));
     }
 
     @SuppressWarnings("unchecked")
diff --git a/server/src/main/java/org/elasticsearch/search/SearchHit.java b/server/src/main/java/org/elasticsearch/search/SearchHit.java
index 35e8813351847..3383227a5b949 100644
--- a/server/src/main/java/org/elasticsearch/search/SearchHit.java
+++ b/server/src/main/java/org/elasticsearch/search/SearchHit.java
@@ -157,8 +157,8 @@ public SearchHit(StreamInput in) throws IOException {
             explanation = readExplanation(in);
         }
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_8_0)) {
-            documentFields.putAll(in.readMap(StreamInput::readString, DocumentField::new));
-            metaFields.putAll(in.readMap(StreamInput::readString, DocumentField::new));
+            documentFields.putAll(in.readMap(DocumentField::new));
+            metaFields.putAll(in.readMap(DocumentField::new));
         } else {
             Map<String, DocumentField> fields = readFields(in);
             fields.forEach(
diff --git a/server/src/main/java/org/elasticsearch/search/aggregations/support/MultiValuesSourceAggregationBuilder.java b/server/src/main/java/org/elasticsearch/search/aggregations/support/MultiValuesSourceAggregationBuilder.java
index b5b5d260e1651..42d1fc745392f 100644
--- a/server/src/main/java/org/elasticsearch/search/aggregations/support/MultiValuesSourceAggregationBuilder.java
+++ b/server/src/main/java/org/elasticsearch/search/aggregations/support/MultiValuesSourceAggregationBuilder.java
@@ -97,7 +97,7 @@ protected MultiValuesSourceAggregationBuilder(StreamInput in) throws IOException
      */
     @SuppressWarnings("unchecked")
     private void read(StreamInput in) throws IOException {
-        fields = in.readMap(StreamInput::readString, MultiValuesSourceFieldConfig::new);
+        fields = in.readMap(MultiValuesSourceFieldConfig::new);
         userValueTypeHint = in.readOptionalWriteable(ValueType::readFromStream);
         format = in.readOptionalString();
     }
diff --git a/server/src/main/java/org/elasticsearch/search/profile/ProfileResult.java b/server/src/main/java/org/elasticsearch/search/profile/ProfileResult.java
index 0fb8c13b14c4e..e34cc1a1bcd77 100644
--- a/server/src/main/java/org/elasticsearch/search/profile/ProfileResult.java
+++ b/server/src/main/java/org/elasticsearch/search/profile/ProfileResult.java
@@ -74,9 +74,9 @@ public ProfileResult(StreamInput in) throws IOException {
         this.type = in.readString();
         this.description = in.readString();
         this.nodeTime = in.readLong();
-        breakdown = in.readMap(StreamInput::readString, StreamInput::readLong);
+        breakdown = in.readMap(StreamInput::readLong);
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_9_0)) {
-            debug = in.readMap(StreamInput::readString, StreamInput::readGenericValue);
+            debug = in.readMap(StreamInput::readGenericValue);
         } else {
             debug = Map.of();
         }
diff --git a/server/src/main/java/org/elasticsearch/search/profile/SearchProfileResults.java b/server/src/main/java/org/elasticsearch/search/profile/SearchProfileResults.java
index 40a251ab24b8d..c993edb5b1dd5 100644
--- a/server/src/main/java/org/elasticsearch/search/profile/SearchProfileResults.java
+++ b/server/src/main/java/org/elasticsearch/search/profile/SearchProfileResults.java
@@ -46,13 +46,10 @@ public SearchProfileResults(Map<String, SearchProfileShardResult> shardResults)
 
     public SearchProfileResults(StreamInput in) throws IOException {
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_16_0)) {
-            shardResults = in.readMap(StreamInput::readString, SearchProfileShardResult::new);
+            shardResults = in.readMap(SearchProfileShardResult::new);
         } else {
             // Before 8.0.0 we only send the query phase result
-            shardResults = in.readMap(
-                StreamInput::readString,
-                i -> new SearchProfileShardResult(new SearchProfileQueryPhaseResult(i), null)
-            );
+            shardResults = in.readMap(i -> new SearchProfileShardResult(new SearchProfileQueryPhaseResult(i), null));
         }
     }
 
diff --git a/server/src/main/java/org/elasticsearch/snapshots/SnapshotInfo.java b/server/src/main/java/org/elasticsearch/snapshots/SnapshotInfo.java
index 4061b79118bef..c16ddd831f78c 100644
--- a/server/src/main/java/org/elasticsearch/snapshots/SnapshotInfo.java
+++ b/server/src/main/java/org/elasticsearch/snapshots/SnapshotInfo.java
@@ -515,10 +515,7 @@ public static SnapshotInfo readFrom(final StreamInput in) throws IOException {
         final Map<String, Object> userMetadata = in.readMap();
         final List<String> dataStreams = in.readImmutableStringList();
         final List<SnapshotFeatureInfo> featureStates = in.readImmutableList(SnapshotFeatureInfo::new);
-        final Map<String, IndexSnapshotDetails> indexSnapshotDetails = in.readImmutableMap(
-            StreamInput::readString,
-            IndexSnapshotDetails::new
-        );
+        final Map<String, IndexSnapshotDetails> indexSnapshotDetails = in.readImmutableMap(IndexSnapshotDetails::new);
         return new SnapshotInfo(
             snapshot,
             indices,
diff --git a/server/src/main/java/org/elasticsearch/tasks/TaskInfo.java b/server/src/main/java/org/elasticsearch/tasks/TaskInfo.java
index 6fd3c1cb0e02e..953ca3b7c101f 100644
--- a/server/src/main/java/org/elasticsearch/tasks/TaskInfo.java
+++ b/server/src/main/java/org/elasticsearch/tasks/TaskInfo.java
@@ -72,7 +72,7 @@ public static TaskInfo from(StreamInput in) throws IOException {
             in.readBoolean(),
             in.readBoolean(),
             TaskId.readFromStream(in),
-            in.readMap(StreamInput::readString, StreamInput::readString)
+            in.readMap(StreamInput::readString)
         );
     }
 
diff --git a/server/src/main/java/org/elasticsearch/upgrades/FeatureMigrationResults.java b/server/src/main/java/org/elasticsearch/upgrades/FeatureMigrationResults.java
index f6f5e7bbc3530..d6f31b6a89ef8 100644
--- a/server/src/main/java/org/elasticsearch/upgrades/FeatureMigrationResults.java
+++ b/server/src/main/java/org/elasticsearch/upgrades/FeatureMigrationResults.java
@@ -69,14 +69,14 @@ public FeatureMigrationResults(Map<String, SingleFeatureMigrationResult> feature
     }
 
     public FeatureMigrationResults(StreamInput in) throws IOException {
-        this.featureStatuses = in.readMap(StreamInput::readString, SingleFeatureMigrationResult::new);
+        this.featureStatuses = in.readMap(SingleFeatureMigrationResult::new);
     }
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
         out.writeMap(
             featureStatuses,
-            (StreamOutput outStream, String featureName) -> outStream.writeString(featureName),
+            StreamOutput::writeString,
             (StreamOutput outStream, SingleFeatureMigrationResult featureStatus) -> featureStatus.writeTo(outStream)
         );
     }
diff --git a/server/src/test/java/org/elasticsearch/common/io/stream/BytesStreamsTests.java b/server/src/test/java/org/elasticsearch/common/io/stream/BytesStreamsTests.java
index 749d8b3c95954..740f72ce02bd6 100644
--- a/server/src/test/java/org/elasticsearch/common/io/stream/BytesStreamsTests.java
+++ b/server/src/test/java/org/elasticsearch/common/io/stream/BytesStreamsTests.java
@@ -562,7 +562,7 @@ public void testWriteMapOfLists() throws IOException {
 
         final StreamInput in = StreamInput.wrap(BytesReference.toBytes(out.bytes()));
 
-        final Map<String, List<String>> loaded = in.readMapOfLists(StreamInput::readString, StreamInput::readString);
+        final Map<String, List<String>> loaded = in.readMapOfLists(StreamInput::readString);
 
         assertThat(loaded.size(), equalTo(expected.size()));
 
diff --git a/server/src/test/java/org/elasticsearch/common/io/stream/RecyclerBytesStreamOutputTests.java b/server/src/test/java/org/elasticsearch/common/io/stream/RecyclerBytesStreamOutputTests.java
index 9c7d8ecf16ff9..63fe28d7fc37b 100644
--- a/server/src/test/java/org/elasticsearch/common/io/stream/RecyclerBytesStreamOutputTests.java
+++ b/server/src/test/java/org/elasticsearch/common/io/stream/RecyclerBytesStreamOutputTests.java
@@ -602,7 +602,7 @@ public void testWriteMapOfLists() throws IOException {
 
         final StreamInput in = StreamInput.wrap(BytesReference.toBytes(out.bytes()));
 
-        final Map<String, List<String>> loaded = in.readMapOfLists(StreamInput::readString, StreamInput::readString);
+        final Map<String, List<String>> loaded = in.readMapOfLists(StreamInput::readString);
 
         assertThat(loaded.size(), equalTo(expected.size()));
 
diff --git a/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/NodeSeekStats.java b/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/NodeSeekStats.java
index 143ff2d344834..db743c1d976e1 100644
--- a/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/NodeSeekStats.java
+++ b/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/NodeSeekStats.java
@@ -31,7 +31,7 @@ public NodeSeekStats(DiscoveryNode node, Map<String, List<ShardSeekStats>> seeks
 
     public NodeSeekStats(StreamInput in) throws IOException {
         super(in);
-        this.seeks = in.readMap(StreamInput::readString, (s -> s.readList(ShardSeekStats::new)));
+        this.seeks = in.readMap(s -> s.readList(ShardSeekStats::new));
     }
 
     @Override
diff --git a/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/ShardSeekStats.java b/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/ShardSeekStats.java
index 8cb290e56f7bf..702d648d1c34d 100644
--- a/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/ShardSeekStats.java
+++ b/test/external-modules/seek-tracking-directory/src/main/java/org/elasticsearch/test/seektracker/ShardSeekStats.java
@@ -20,7 +20,7 @@
 public record ShardSeekStats(String shard, Map<String, Long> seeksPerFile) implements Writeable, ToXContentObject {
 
     public ShardSeekStats(StreamInput in) throws IOException {
-        this(in.readString(), in.readMap(StreamInput::readString, StreamInput::readLong));
+        this(in.readString(), in.readMap(StreamInput::readLong));
     }
 
     @Override
diff --git a/x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/stringstats/InternalStringStats.java b/x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/stringstats/InternalStringStats.java
index a0c4ba5866702..f5c1fbbb83bf3 100644
--- a/x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/stringstats/InternalStringStats.java
+++ b/x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/stringstats/InternalStringStats.java
@@ -93,7 +93,7 @@ public InternalStringStats(StreamInput in) throws IOException {
         totalLength = in.readVLong();
         minLength = in.readVInt();
         maxLength = in.readVInt();
-        charOccurrences = in.readMap(StreamInput::readString, StreamInput::readLong);
+        charOccurrences = in.readMap(StreamInput::readLong);
     }
 
     @Override
diff --git a/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/action/GetAutoscalingCapacityAction.java b/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/action/GetAutoscalingCapacityAction.java
index 0d34cd5da4f88..029729f9cad12 100644
--- a/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/action/GetAutoscalingCapacityAction.java
+++ b/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/action/GetAutoscalingCapacityAction.java
@@ -85,7 +85,7 @@ public Response(final SortedMap<String, AutoscalingDeciderResults> results) {
 
         public Response(final StreamInput in) throws IOException {
             super(in);
-            results = new TreeMap<>(in.readMap(StreamInput::readString, AutoscalingDeciderResults::new));
+            results = new TreeMap<>(in.readMap(AutoscalingDeciderResults::new));
         }
 
         @Override
diff --git a/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/capacity/AutoscalingDeciderResults.java b/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/capacity/AutoscalingDeciderResults.java
index ab4b9bebc125a..b45a38614a1b7 100644
--- a/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/capacity/AutoscalingDeciderResults.java
+++ b/x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/capacity/AutoscalingDeciderResults.java
@@ -64,7 +64,7 @@ public AutoscalingDeciderResults(final StreamInput in) throws IOException {
         this.currentNodes = in.readSet(DiscoveryNode::new)
             .stream()
             .collect(Collectors.toCollection(() -> new TreeSet<>(DISCOVERY_NODE_COMPARATOR)));
-        this.results = new TreeMap<>(in.readMap(StreamInput::readString, AutoscalingDeciderResult::new));
+        this.results = new TreeMap<>(in.readMap(AutoscalingDeciderResult::new));
     }
 
     @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTiersFeatureSetUsage.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTiersFeatureSetUsage.java
index ec3d9f2631110..8ec138948f2f1 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTiersFeatureSetUsage.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/DataTiersFeatureSetUsage.java
@@ -32,7 +32,7 @@ public class DataTiersFeatureSetUsage extends XPackFeatureSet.Usage {
 
     public DataTiersFeatureSetUsage(StreamInput in) throws IOException {
         super(in);
-        this.tierStats = in.readMap(StreamInput::readString, TierSpecificStats::new);
+        this.tierStats = in.readMap(TierSpecificStats::new);
     }
 
     public DataTiersFeatureSetUsage(Map<String, TierSpecificStats> tierStats) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowMetadata.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowMetadata.java
index deb46fc97db2e..822b3829a4e94 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowMetadata.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowMetadata.java
@@ -106,9 +106,9 @@ public AutoFollowMetadata(
 
     public AutoFollowMetadata(StreamInput in) throws IOException {
         this(
-            in.readMap(StreamInput::readString, AutoFollowPattern::readFrom),
-            in.readMapOfLists(StreamInput::readString, StreamInput::readString),
-            in.readMap(StreamInput::readString, valIn -> valIn.readMap(StreamInput::readString, StreamInput::readString))
+            in.readMap(AutoFollowPattern::readFrom),
+            in.readMapOfLists(StreamInput::readString),
+            in.readMap(valIn -> valIn.readMap(StreamInput::readString))
         );
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowStats.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowStats.java
index debf4dc65f78b..da83545d3a327 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowStats.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/AutoFollowStats.java
@@ -124,10 +124,8 @@ public AutoFollowStats(StreamInput in) throws IOException {
         numberOfFailedFollowIndices = in.readVLong();
         numberOfFailedRemoteClusterStateRequests = in.readVLong();
         numberOfSuccessfulFollowIndices = in.readVLong();
-        recentAutoFollowErrors = new TreeMap<>(
-            in.readMap(StreamInput::readString, in1 -> new Tuple<>(in1.readZLong(), in1.readException()))
-        );
-        autoFollowedClusters = new TreeMap<>(in.readMap(StreamInput::readString, AutoFollowedCluster::new));
+        recentAutoFollowErrors = new TreeMap<>(in.readMap(in1 -> new Tuple<>(in1.readZLong(), in1.readException())));
+        autoFollowedClusters = new TreeMap<>(in.readMap(AutoFollowedCluster::new));
     }
 
     @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/GetAutoFollowPatternAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/GetAutoFollowPatternAction.java
index ddab94431f29f..cfe46f8161b1f 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/GetAutoFollowPatternAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/GetAutoFollowPatternAction.java
@@ -88,7 +88,7 @@ public Map<String, AutoFollowPattern> getAutoFollowPatterns() {
 
         public Response(StreamInput in) throws IOException {
             super(in);
-            autoFollowPatterns = in.readMap(StreamInput::readString, AutoFollowPattern::readFrom);
+            autoFollowPatterns = in.readMap(AutoFollowPattern::readFrom);
         }
 
         @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/ShardFollowTask.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/ShardFollowTask.java
index fc0cb00e443d4..b1d6c5583afa2 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/ShardFollowTask.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ccr/action/ShardFollowTask.java
@@ -122,7 +122,7 @@ private ShardFollowTask(String remoteCluster, ShardId followShardId, ShardId lea
         this.remoteCluster = remoteCluster;
         this.followShardId = followShardId;
         this.leaderShardId = leaderShardId;
-        this.headers = in.readImmutableMap(StreamInput::readString, StreamInput::readString);
+        this.headers = in.readImmutableMap(StreamInput::readString);
     }
 
     public String getRemoteCluster() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/enrich/EnrichMetadata.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/enrich/EnrichMetadata.java
index 042f8a975da42..6908c4f9f72d6 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/enrich/EnrichMetadata.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/enrich/EnrichMetadata.java
@@ -65,7 +65,7 @@ public static EnrichMetadata fromXContent(XContentParser parser) throws IOExcept
     private final Map<String, EnrichPolicy> policies;
 
     public EnrichMetadata(StreamInput in) throws IOException {
-        this(in.readMap(StreamInput::readString, EnrichPolicy::new));
+        this(in.readMap(EnrichPolicy::new));
     }
 
     public EnrichMetadata(Map<String, EnrichPolicy> policies) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleFeatureSetUsage.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleFeatureSetUsage.java
index 882c1e91da026..19bc639a7e595 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleFeatureSetUsage.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleFeatureSetUsage.java
@@ -105,7 +105,7 @@ public PolicyStats(Map<String, PhaseStats> phaseStats, int numberIndicesManaged)
         }
 
         public PolicyStats(StreamInput in) throws IOException {
-            this.phaseStats = in.readMap(StreamInput::readString, PhaseStats::new);
+            this.phaseStats = in.readMap(PhaseStats::new);
             this.indicesManaged = in.readVInt();
         }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/LifecyclePolicy.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/LifecyclePolicy.java
index c2d2303a3a4a5..4beebbe971440 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/LifecyclePolicy.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/LifecyclePolicy.java
@@ -101,7 +101,7 @@ public LifecyclePolicy(String name, Map<String, Phase> phases, @Nullable Map<Str
     public LifecyclePolicy(StreamInput in) throws IOException {
         type = in.readNamedWriteable(LifecycleType.class);
         name = in.readString();
-        phases = in.readImmutableMap(StreamInput::readString, Phase::new);
+        phases = in.readImmutableMap(Phase::new);
         this.metadata = in.readMap();
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/EstimateModelMemoryAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/EstimateModelMemoryAction.java
index 3220932262641..0348db4a218fe 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/EstimateModelMemoryAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/EstimateModelMemoryAction.java
@@ -74,8 +74,8 @@ public Request() {
         public Request(StreamInput in) throws IOException {
             super(in);
             this.analysisConfig = in.readBoolean() ? new AnalysisConfig(in) : null;
-            this.overallCardinality = in.readMap(StreamInput::readString, StreamInput::readVLong);
-            this.maxBucketCardinality = in.readMap(StreamInput::readString, StreamInput::readVLong);
+            this.overallCardinality = in.readMap(StreamInput::readVLong);
+            this.maxBucketCardinality = in.readMap(StreamInput::readVLong);
         }
 
         @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/GetDatafeedRunningStateAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/GetDatafeedRunningStateAction.java
index f26f0c29c7815..8b9aa5f0c0c34 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/GetDatafeedRunningStateAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/GetDatafeedRunningStateAction.java
@@ -161,7 +161,7 @@ public static Response fromTaskAndState(String datafeedId, RunningState runningS
 
         public Response(StreamInput in) throws IOException {
             super(in);
-            datafeedRunningState = in.readMap(StreamInput::readString, RunningState::new);
+            datafeedRunningState = in.readMap(RunningState::new);
         }
 
         public Response(Map<String, RunningState> runtimeStateMap) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedConfig.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedConfig.java
index 4185b16eb1444..699d6d3b02397 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedConfig.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedConfig.java
@@ -295,7 +295,7 @@ public DatafeedConfig(StreamInput in) throws IOException {
         }
         this.scrollSize = in.readOptionalVInt();
         this.chunkingConfig = in.readOptionalWriteable(ChunkingConfig::new);
-        this.headers = in.readImmutableMap(StreamInput::readString, StreamInput::readString);
+        this.headers = in.readImmutableMap(StreamInput::readString);
         delayedDataCheckConfig = in.readOptionalWriteable(DelayedDataCheckConfig::new);
         maxEmptySearches = in.readOptionalVInt();
         indicesOptions = IndicesOptions.readIndicesOptions(in);
@@ -808,7 +808,7 @@ public Builder(StreamInput in) throws IOException {
             }
             this.scrollSize = in.readOptionalVInt();
             this.chunkingConfig = in.readOptionalWriteable(ChunkingConfig::new);
-            this.headers = in.readImmutableMap(StreamInput::readString, StreamInput::readString);
+            this.headers = in.readImmutableMap(StreamInput::readString);
             delayedDataCheckConfig = in.readOptionalWriteable(DelayedDataCheckConfig::new);
             maxEmptySearches = in.readOptionalVInt();
             if (in.readBoolean()) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/dataframe/DataFrameAnalyticsConfig.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/dataframe/DataFrameAnalyticsConfig.java
index 3095c1470faf1..49759f2ec358e 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/dataframe/DataFrameAnalyticsConfig.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/dataframe/DataFrameAnalyticsConfig.java
@@ -186,7 +186,7 @@ public DataFrameAnalyticsConfig(StreamInput in) throws IOException {
         this.analysis = in.readNamedWriteable(DataFrameAnalysis.class);
         this.analyzedFields = in.readOptionalWriteable(FetchSourceContext::readFrom);
         this.modelMemoryLimit = in.readOptionalWriteable(ByteSizeValue::readFrom);
-        this.headers = in.readImmutableMap(StreamInput::readString, StreamInput::readString);
+        this.headers = in.readImmutableMap(StreamInput::readString);
         this.createTime = in.readOptionalInstant();
         this.version = in.readBoolean() ? Version.readVersion(in) : null;
         this.allowLazyStart = in.readBoolean();
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfig.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfig.java
index 17a59fd1042c8..900a62772c31c 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfig.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/TrainedModelConfig.java
@@ -256,7 +256,7 @@ public TrainedModelConfig(StreamInput in) throws IOException {
         modelSize = in.readVLong();
         estimatedOperations = in.readVLong();
         licenseLevel = License.OperationMode.parse(in.readString());
-        this.defaultFieldMap = in.readBoolean() ? in.readImmutableMap(StreamInput::readString, StreamInput::readString) : null;
+        this.defaultFieldMap = in.readBoolean() ? in.readImmutableMap(StreamInput::readString) : null;
 
         this.inferenceConfig = in.readOptionalNamedWriteable(InferenceConfig.class);
         if (in.getTransportVersion().onOrAfter(VERSION_3RD_PARTY_CONFIG_ADDED)) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/FrequencyEncoding.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/FrequencyEncoding.java
index 5c059d4ef6a0e..034b6721ec1ec 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/FrequencyEncoding.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/FrequencyEncoding.java
@@ -86,7 +86,7 @@ public FrequencyEncoding(String field, String featureName, Map<String, Double> f
     public FrequencyEncoding(StreamInput in) throws IOException {
         this.field = in.readString();
         this.featureName = in.readString();
-        this.frequencyMap = in.readImmutableMap(StreamInput::readString, StreamInput::readDouble);
+        this.frequencyMap = in.readImmutableMap(StreamInput::readDouble);
         this.custom = in.readBoolean();
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/OneHotEncoding.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/OneHotEncoding.java
index ba2c802c9addb..cd0a91466dced 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/OneHotEncoding.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/OneHotEncoding.java
@@ -74,7 +74,7 @@ public OneHotEncoding(String field, Map<String, String> hotMap, Boolean custom)
 
     public OneHotEncoding(StreamInput in) throws IOException {
         this.field = in.readString();
-        this.hotMap = Collections.unmodifiableMap(new TreeMap<>(in.readMap(StreamInput::readString, StreamInput::readString)));
+        this.hotMap = Collections.unmodifiableMap(new TreeMap<>(in.readMap(StreamInput::readString)));
         this.custom = in.readBoolean();
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/TargetMeanEncoding.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/TargetMeanEncoding.java
index 8ed2560bbdd7b..ac69bec04c619 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/TargetMeanEncoding.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/inference/preprocessing/TargetMeanEncoding.java
@@ -90,7 +90,7 @@ public TargetMeanEncoding(String field, String featureName, Map<String, Double>
     public TargetMeanEncoding(StreamInput in) throws IOException {
         this.field = in.readString();
         this.featureName = in.readString();
-        this.meanMap = in.readImmutableMap(StreamInput::readString, StreamInput::readDouble);
+        this.meanMap = in.readImmutableMap(StreamInput::readDouble);
         this.defaultValue = in.readDouble();
         this.custom = in.readBoolean();
     }
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/RuleScope.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/RuleScope.java
index faec24fbf966b..24b4d324cd894 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/RuleScope.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/config/RuleScope.java
@@ -68,7 +68,7 @@ public RuleScope(Map<String, FilterRef> scope) {
     }
 
     public RuleScope(StreamInput in) throws IOException {
-        scope = in.readMap(StreamInput::readString, FilterRef::new);
+        scope = in.readMap(FilterRef::new);
     }
 
     @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/stats/CountAccumulator.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/stats/CountAccumulator.java
index 98c07ccdf4d64..60e4f748df217 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/stats/CountAccumulator.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/stats/CountAccumulator.java
@@ -37,7 +37,7 @@ private CountAccumulator(Map<String, Long> counts) {
     }
 
     public CountAccumulator(StreamInput in) throws IOException {
-        this.counts = in.readMap(StreamInput::readString, StreamInput::readLong);
+        this.counts = in.readMap(StreamInput::readLong);
     }
 
     public void merge(CountAccumulator other) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupCapsAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupCapsAction.java
index 5bc9e44da3366..86e3720468c79 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupCapsAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupCapsAction.java
@@ -116,7 +116,7 @@ public Response(Map<String, RollableIndexCaps> jobs) {
         }
 
         Response(StreamInput in) throws IOException {
-            jobs = in.readImmutableMap(StreamInput::readString, RollableIndexCaps::new);
+            jobs = in.readImmutableMap(RollableIndexCaps::new);
         }
 
         public Map<String, RollableIndexCaps> getJobs() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupIndexCapsAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupIndexCapsAction.java
index 4fd7d244c7d11..cd5be88bf7b7c 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupIndexCapsAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/GetRollupIndexCapsAction.java
@@ -145,7 +145,7 @@ public Response(Map<String, RollableIndexCaps> jobs) {
         }
 
         Response(StreamInput in) throws IOException {
-            jobs = in.readMap(StreamInput::readString, RollableIndexCaps::new);
+            jobs = in.readMap(RollableIndexCaps::new);
         }
 
         public Map<String, RollableIndexCaps> getJobs() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/RollupJobCaps.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/RollupJobCaps.java
index 768613b2e51ec..f11e56edf5449 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/RollupJobCaps.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/action/RollupJobCaps.java
@@ -70,7 +70,7 @@ public RollupJobCaps(StreamInput in) throws IOException {
         this.jobID = in.readString();
         this.rollupIndex = in.readString();
         this.indexPattern = in.readString();
-        this.fieldCapLookup = in.readMap(StreamInput::readString, RollupFieldCaps::new);
+        this.fieldCapLookup = in.readMap(RollupFieldCaps::new);
     }
 
     public Map<String, RollupFieldCaps> getFieldCaps() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/job/RollupJob.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/job/RollupJob.java
index 9566366b74beb..683f39be9cc98 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/job/RollupJob.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/rollup/job/RollupJob.java
@@ -57,7 +57,7 @@ public RollupJob(RollupJobConfig config, Map<String, String> headers) {
 
     public RollupJob(StreamInput in) throws IOException {
         this.config = new RollupJobConfig(in);
-        headers = in.readMap(StreamInput::readString, StreamInput::readString);
+        headers = in.readMap(StreamInput::readString);
     }
 
     public RollupJobConfig getConfig() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/apikey/BulkUpdateApiKeyResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/apikey/BulkUpdateApiKeyResponse.java
index c6b9822b2ae75..c6d2c07f70127 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/apikey/BulkUpdateApiKeyResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/apikey/BulkUpdateApiKeyResponse.java
@@ -37,7 +37,7 @@ public BulkUpdateApiKeyResponse(StreamInput in) throws IOException {
         super(in);
         this.updated = in.readStringList();
         this.noops = in.readStringList();
-        this.errorDetails = in.readMap(StreamInput::readString, StreamInput::readException);
+        this.errorDetails = in.readMap(StreamInput::readException);
     }
 
     public List<String> getUpdated() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/privilege/PutPrivilegesResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/privilege/PutPrivilegesResponse.java
index 3bb73a58c0c69..6a5b9646dc0f8 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/privilege/PutPrivilegesResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/privilege/PutPrivilegesResponse.java
@@ -27,7 +27,7 @@ public final class PutPrivilegesResponse extends ActionResponse implements ToXCo
 
     public PutPrivilegesResponse(StreamInput in) throws IOException {
         super(in);
-        this.created = in.readImmutableMap(StreamInput::readString, StreamInput::readStringList);
+        this.created = in.readImmutableMap(StreamInput::readStringList);
     }
 
     public PutPrivilegesResponse(Map<String, List<String>> created) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/GetProfilesResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/GetProfilesResponse.java
index 5dce557821110..08239f2a1d4b9 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/GetProfilesResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/GetProfilesResponse.java
@@ -32,7 +32,7 @@ public GetProfilesResponse(List<Profile> profiles, Map<String, Exception> errors
     public GetProfilesResponse(StreamInput in) throws IOException {
         super(in);
         this.profiles = in.readImmutableList(Profile::new);
-        this.errors = in.readMap(StreamInput::readString, StreamInput::readException);
+        this.errors = in.readMap(StreamInput::readException);
     }
 
     public List<Profile> getProfiles() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/SuggestProfilesRequest.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/SuggestProfilesRequest.java
index 3df1b77eac498..dddcef16a455f 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/SuggestProfilesRequest.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/profile/SuggestProfilesRequest.java
@@ -140,7 +140,7 @@ public Hint(List<String> uids, Map<String, Object> labelsInput) {
 
         public Hint(StreamInput in) throws IOException {
             this.uids = in.readStringList();
-            this.labels = in.readMapOfLists(StreamInput::readString, StreamInput::readString);
+            this.labels = in.readMapOfLists(StreamInput::readString);
         }
 
         public List<String> getUids() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/GetUsersResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/GetUsersResponse.java
index 1c3a1fa869063..6095a05cd5336 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/GetUsersResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/GetUsersResponse.java
@@ -45,7 +45,7 @@ public GetUsersResponse(StreamInput in) throws IOException {
         }
         if (in.getTransportVersion().onOrAfter(TransportVersion.V_8_5_0)) {
             if (in.readBoolean()) {
-                profileUidLookup = in.readMap(StreamInput::readString, StreamInput::readString);
+                profileUidLookup = in.readMap(StreamInput::readString);
             } else {
                 profileUidLookup = null;
             }
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/HasPrivilegesResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/HasPrivilegesResponse.java
index fc2f5e0579d03..073e639715bce 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/HasPrivilegesResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/HasPrivilegesResponse.java
@@ -40,9 +40,9 @@ public HasPrivilegesResponse() {
     public HasPrivilegesResponse(StreamInput in) throws IOException {
         super(in);
         completeMatch = in.readBoolean();
-        cluster = in.readMap(StreamInput::readString, StreamInput::readBoolean);
+        cluster = in.readMap(StreamInput::readBoolean);
         index = readResourcePrivileges(in);
-        application = in.readMap(StreamInput::readString, HasPrivilegesResponse::readResourcePrivileges);
+        application = in.readMap(HasPrivilegesResponse::readResourcePrivileges);
         username = in.readString();
     }
 
@@ -119,7 +119,7 @@ private static Set<ResourcePrivileges> readResourcePrivileges(StreamInput in) th
         final Set<ResourcePrivileges> set = new TreeSet<>(Comparator.comparing(o -> o.getResource()));
         for (int i = 0; i < count; i++) {
             final String index = in.readString();
-            final Map<String, Boolean> privileges = in.readMap(StreamInput::readString, StreamInput::readBoolean);
+            final Map<String, Boolean> privileges = in.readMap(StreamInput::readBoolean);
             set.add(ResourcePrivileges.builder(index).addPrivileges(privileges).build());
         }
         return set;
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/ProfileHasPrivilegesResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/ProfileHasPrivilegesResponse.java
index 0f2380f1c0fb2..c3e20d4d6e4e9 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/ProfileHasPrivilegesResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/user/ProfileHasPrivilegesResponse.java
@@ -27,7 +27,7 @@ public class ProfileHasPrivilegesResponse extends ActionResponse implements ToXC
     public ProfileHasPrivilegesResponse(StreamInput in) throws IOException {
         super(in);
         this.hasPrivilegeUids = in.readSet(StreamInput::readString);
-        this.errors = in.readMap(StreamInput::readString, StreamInput::readException);
+        this.errors = in.readMap(StreamInput::readException);
     }
 
     public ProfileHasPrivilegesResponse(Set<String> hasPrivilegeUids, Map<String, Exception> errors) {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleMetadata.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleMetadata.java
index 49f9b73bff055..5f1483e4c6004 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleMetadata.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleMetadata.java
@@ -93,7 +93,7 @@ public SnapshotLifecycleMetadata(
     }
 
     public SnapshotLifecycleMetadata(StreamInput in) throws IOException {
-        this.snapshotConfigurations = in.readMap(StreamInput::readString, SnapshotLifecyclePolicyMetadata::new);
+        this.snapshotConfigurations = in.readMap(SnapshotLifecyclePolicyMetadata::new);
         this.operationMode = in.readEnum(OperationMode.class);
         this.slmStats = new SnapshotLifecycleStats(in);
     }
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleStats.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleStats.java
index c7fc42b18dbeb..10ab898b34f71 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleStats.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/slm/SnapshotLifecycleStats.java
@@ -98,7 +98,7 @@ public SnapshotLifecycleStats(
     }
 
     public SnapshotLifecycleStats(StreamInput in) throws IOException {
-        this.policyStats = new ConcurrentHashMap<>(in.readMap(StreamInput::readString, SnapshotPolicyStats::new));
+        this.policyStats = new ConcurrentHashMap<>(in.readMap(SnapshotPolicyStats::new));
         this.retentionRunCount.inc(in.readVLong());
         this.retentionFailedCount.inc(in.readVLong());
         this.retentionTimedOut.inc(in.readVLong());
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/textstructure/structurefinder/TextStructure.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/textstructure/structurefinder/TextStructure.java
index 4835bc717fc58..1a5e23b0ca18c 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/textstructure/structurefinder/TextStructure.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/textstructure/structurefinder/TextStructure.java
@@ -237,7 +237,7 @@ public TextStructure(StreamInput in) throws IOException {
         needClientTimezone = in.readBoolean();
         mappings = Collections.unmodifiableSortedMap(new TreeMap<>(in.readMap()));
         ingestPipeline = in.readBoolean() ? Collections.unmodifiableMap(in.readMap()) : null;
-        fieldStats = Collections.unmodifiableSortedMap(new TreeMap<>(in.readMap(StreamInput::readString, FieldStats::new)));
+        fieldStats = Collections.unmodifiableSortedMap(new TreeMap<>(in.readMap(FieldStats::new)));
         explanation = in.readImmutableList(StreamInput::readString);
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/TransformFeatureSetUsage.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/TransformFeatureSetUsage.java
index 0941c4667bb7f..5d58284daa2b6 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/TransformFeatureSetUsage.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/TransformFeatureSetUsage.java
@@ -31,8 +31,8 @@ public class TransformFeatureSetUsage extends Usage {
 
     public TransformFeatureSetUsage(StreamInput in) throws IOException {
         super(in);
-        this.transformCountByState = in.readMap(StreamInput::readString, StreamInput::readLong);
-        this.transformCountByFeature = in.readMap(StreamInput::readString, StreamInput::readLong);
+        this.transformCountByState = in.readMap(StreamInput::readLong);
+        this.transformCountByFeature = in.readMap(StreamInput::readLong);
         this.accumulatedStats = new TransformIndexerStats(in);
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/action/ValidateTransformAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/action/ValidateTransformAction.java
index 48b18606d024b..3b5163dbf4c2d 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/action/ValidateTransformAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/action/ValidateTransformAction.java
@@ -105,7 +105,7 @@ public Response(Map<String, String> destIndexMappings) {
         }
 
         public Response(StreamInput in) throws IOException {
-            this.destIndexMappings = in.readMap(StreamInput::readString, StreamInput::readString);
+            this.destIndexMappings = in.readMap(StreamInput::readString);
         }
 
         @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/NodeAttributes.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/NodeAttributes.java
index 1192260f78013..3cf91be019b60 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/NodeAttributes.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/NodeAttributes.java
@@ -83,7 +83,7 @@ public NodeAttributes(StreamInput in) throws IOException {
         this.name = in.readString();
         this.ephemeralId = in.readString();
         this.transportAddress = in.readString();
-        this.attributes = in.readImmutableMap(StreamInput::readString, StreamInput::readString);
+        this.attributes = in.readImmutableMap(StreamInput::readString);
     }
 
     /**
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfig.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfig.java
index b82569e4f911d..853313ea60cec 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfig.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfig.java
@@ -247,7 +247,7 @@ public TransformConfig(final StreamInput in) throws IOException {
         source = new SourceConfig(in);
         dest = new DestConfig(in);
         frequency = in.readOptionalTimeValue();
-        setHeaders(in.readMap(StreamInput::readString, StreamInput::readString));
+        setHeaders(in.readMap(StreamInput::readString));
         pivotConfig = in.readOptionalWriteable(PivotConfig::new);
         latestConfig = in.readOptionalWriteable(LatestConfig::new);
         description = in.readOptionalString();
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfigUpdate.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfigUpdate.java
index 25e25dfe80e0f..6ac924fe87e8c 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfigUpdate.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/transforms/TransformConfigUpdate.java
@@ -114,7 +114,7 @@ public TransformConfigUpdate(final StreamInput in) throws IOException {
         description = in.readOptionalString();
         syncConfig = in.readOptionalNamedWriteable(SyncConfig.class);
         if (in.readBoolean()) {
-            setHeaders(in.readMap(StreamInput::readString, StreamInput::readString));
+            setHeaders(in.readMap(StreamInput::readString));
         }
         settings = in.readOptionalWriteable(SettingsConfig::new);
         metadata = in.readMap();
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/watch/WatchStatus.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/watch/WatchStatus.java
index a59c463e48fe9..719c97e249113 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/watch/WatchStatus.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/watch/WatchStatus.java
@@ -72,7 +72,7 @@ public WatchStatus(StreamInput in) throws IOException {
             executionState = ExecutionState.resolve(in.readString());
         }
         if (in.readBoolean()) {
-            headers = in.readMap(StreamInput::readString, StreamInput::readString);
+            headers = in.readMap(StreamInput::readString);
         } else {
             headers = Collections.emptyMap();
         }
diff --git a/x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationInfoAction.java b/x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationInfoAction.java
index 931e039ca968a..1a6f11fa32514 100644
--- a/x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationInfoAction.java
+++ b/x-pack/plugin/deprecation/src/main/java/org/elasticsearch/xpack/deprecation/DeprecationInfoAction.java
@@ -153,13 +153,13 @@ public Response(StreamInput in) throws IOException {
             super(in);
             clusterSettingsIssues = in.readList(DeprecationIssue::new);
             nodeSettingsIssues = in.readList(DeprecationIssue::new);
-            indexSettingsIssues = in.readMapOfLists(StreamInput::readString, DeprecationIssue::new);
+            indexSettingsIssues = in.readMapOfLists(DeprecationIssue::new);
             if (in.getTransportVersion().before(TransportVersion.V_7_11_0)) {
                 List<DeprecationIssue> mlIssues = in.readList(DeprecationIssue::new);
                 pluginSettingsIssues = new HashMap<>();
                 pluginSettingsIssues.put("ml_settings", mlIssues);
             } else {
-                pluginSettingsIssues = in.readMapOfLists(StreamInput::readString, DeprecationIssue::new);
+                pluginSettingsIssues = in.readMapOfLists(DeprecationIssue::new);
             }
         }
 
diff --git a/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java b/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java
index 27a31dd19004b..12dc9e52daf53 100644
--- a/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java
+++ b/x-pack/plugin/ent-search/src/main/java/org/elasticsearch/xpack/application/analytics/action/PostAnalyticsEventAction.java
@@ -90,7 +90,7 @@ public Request(StreamInput in) throws IOException {
             this.eventTime = in.readLong();
             this.xContentType = in.readEnum(XContentType.class);
             this.payload = in.readBytesReference();
-            this.headers = in.readMap(StreamInput::readString, StreamInput::readStringList);
+            this.headers = in.readMap(StreamInput::readStringList);
             this.clientAddress = in.readOptionalString();
         }
 
diff --git a/x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/action/EqlSearchResponse.java b/x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/action/EqlSearchResponse.java
index 63062b5f48511..308363200c866 100644
--- a/x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/action/EqlSearchResponse.java
+++ b/x-pack/plugin/eql/src/main/java/org/elasticsearch/xpack/eql/action/EqlSearchResponse.java
@@ -257,7 +257,7 @@ public Event(StreamInput in) throws IOException {
             id = in.readString();
             source = in.readBytesReference();
             if (in.getTransportVersion().onOrAfter(TransportVersion.V_7_13_0) && in.readBoolean()) {
-                fetchFields = in.readMap(StreamInput::readString, DocumentField::new);
+                fetchFields = in.readMap(DocumentField::new);
             } else {
                 fetchFields = null;
             }
diff --git a/x-pack/plugin/logstash/src/main/java/org/elasticsearch/xpack/logstash/action/GetPipelineResponse.java b/x-pack/plugin/logstash/src/main/java/org/elasticsearch/xpack/logstash/action/GetPipelineResponse.java
index e10b9183520bc..f28edd25bf483 100644
--- a/x-pack/plugin/logstash/src/main/java/org/elasticsearch/xpack/logstash/action/GetPipelineResponse.java
+++ b/x-pack/plugin/logstash/src/main/java/org/elasticsearch/xpack/logstash/action/GetPipelineResponse.java
@@ -29,7 +29,7 @@ public GetPipelineResponse(Map<String, BytesReference> pipelines) {
 
     public GetPipelineResponse(StreamInput in) throws IOException {
         super(in);
-        this.pipelines = in.readMap(StreamInput::readString, StreamInput::readBytesReference);
+        this.pipelines = in.readMap(StreamInput::readBytesReference);
     }
 
     public Map<String, BytesReference> pipelines() {
diff --git a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/FrequentItemSetCollector.java b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/FrequentItemSetCollector.java
index 0b04240e89706..397ddae669aa3 100644
--- a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/FrequentItemSetCollector.java
+++ b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/FrequentItemSetCollector.java
@@ -59,7 +59,7 @@ public FrequentItemSet(Map<String, List<Object>> fields, long docCount, double s
         }
 
         public FrequentItemSet(StreamInput in) throws IOException {
-            this.fields = in.readMapOfLists(StreamInput::readString, StreamInput::readGenericValue);
+            this.fields = in.readMapOfLists(StreamInput::readGenericValue);
             this.docCount = in.readVLong();
             this.support = in.readDouble();
         }
diff --git a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/inference/InferencePipelineAggregationBuilder.java b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/inference/InferencePipelineAggregationBuilder.java
index ccff6ae21e0b3..e416f981dda64 100644
--- a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/inference/InferencePipelineAggregationBuilder.java
+++ b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/inference/InferencePipelineAggregationBuilder.java
@@ -166,7 +166,7 @@ public InferencePipelineAggregationBuilder(
     ) throws IOException {
         super(in, NAME);
         modelId = in.readString();
-        bucketPathMap = in.readMap(StreamInput::readString, StreamInput::readString);
+        bucketPathMap = in.readMap(StreamInput::readString);
         inferenceConfig = in.readOptionalNamedWriteable(InferenceConfigUpdate.class);
         this.modelLoadingService = modelLoadingService;
         this.model = null;
diff --git a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/kstest/InternalKSTestAggregation.java b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/kstest/InternalKSTestAggregation.java
index 632919bc7ff30..b67acc4c1eba4 100644
--- a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/kstest/InternalKSTestAggregation.java
+++ b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/aggs/kstest/InternalKSTestAggregation.java
@@ -30,7 +30,7 @@ public InternalKSTestAggregation(String name, Map<String, Object> metadata, Map<
 
     public InternalKSTestAggregation(StreamInput in) throws IOException {
         super(in);
-        this.modeValues = in.readMap(StreamInput::readString, StreamInput::readDouble);
+        this.modeValues = in.readMap(StreamInput::readDouble);
     }
 
     @Override
diff --git a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/ModelAliasMetadata.java b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/ModelAliasMetadata.java
index 755121af95ea6..9e4018cb2747a 100644
--- a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/ModelAliasMetadata.java
+++ b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/ModelAliasMetadata.java
@@ -83,7 +83,7 @@ public ModelAliasMetadata(Map<String, ModelAliasEntry> modelAliases) {
     }
 
     public ModelAliasMetadata(StreamInput in) throws IOException {
-        this.modelAliases = in.readImmutableMap(StreamInput::readString, ModelAliasEntry::new);
+        this.modelAliases = in.readImmutableMap(ModelAliasEntry::new);
     }
 
     public Map<String, ModelAliasEntry> modelAliases() {
diff --git a/x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/mr/InternalItemSetMapReduceAggregationTests.java b/x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/mr/InternalItemSetMapReduceAggregationTests.java
index 837b6b4a06c60..ddf2071ec3511 100644
--- a/x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/mr/InternalItemSetMapReduceAggregationTests.java
+++ b/x-pack/plugin/ml/src/test/java/org/elasticsearch/xpack/ml/aggs/frequentitemsets/mr/InternalItemSetMapReduceAggregationTests.java
@@ -72,7 +72,7 @@ static class WordCounts implements ToXContent, Writeable, Closeable {
             }
 
             WordCounts(StreamInput in) throws IOException {
-                this.frequencies = in.readMap(StreamInput::readString, StreamInput::readLong);
+                this.frequencies = in.readMap(StreamInput::readLong);
             }
 
             @Override
diff --git a/x-pack/plugin/profiler/src/main/java/org/elasticsearch/xpack/profiler/GetProfilingResponse.java b/x-pack/plugin/profiler/src/main/java/org/elasticsearch/xpack/profiler/GetProfilingResponse.java
index cc2f34a18adf4..1962b31af2cf6 100644
--- a/x-pack/plugin/profiler/src/main/java/org/elasticsearch/xpack/profiler/GetProfilingResponse.java
+++ b/x-pack/plugin/profiler/src/main/java/org/elasticsearch/xpack/profiler/GetProfilingResponse.java
@@ -37,7 +37,6 @@ public class GetProfilingResponse extends ActionResponse implements ChunkedToXCo
     public GetProfilingResponse(StreamInput in) throws IOException {
         this.stackTraces = in.readBoolean()
             ? in.readMap(
-                StreamInput::readString,
                 i -> new StackTrace(
                     i.readList(StreamInput::readInt),
                     i.readList(StreamInput::readString),
@@ -48,7 +47,6 @@ public GetProfilingResponse(StreamInput in) throws IOException {
             : null;
         this.stackFrames = in.readBoolean()
             ? in.readMap(
-                StreamInput::readString,
                 i -> new StackFrame(
                     i.readList(StreamInput::readString),
                     i.readList(StreamInput::readString),
@@ -57,8 +55,8 @@ public GetProfilingResponse(StreamInput in) throws IOException {
                 )
             )
             : null;
-        this.executables = in.readBoolean() ? in.readMap(StreamInput::readString, StreamInput::readString) : null;
-        this.stackTraceEvents = in.readBoolean() ? in.readMap(StreamInput::readString, StreamInput::readInt) : null;
+        this.executables = in.readBoolean() ? in.readMap(StreamInput::readString) : null;
+        this.stackTraceEvents = in.readBoolean() ? in.readMap(StreamInput::readInt) : null;
         this.totalFrames = in.readInt();
         this.samplingRate = in.readDouble();
     }