database-case-mysql_cassandra

MySQL

Reason: ACID - https://dev.mysql.com/doc/refman/5.6/en/mysql-acid.html
Data: billing information, trasaction information, user information
Solution: use at least two MySQL, one for main, the other as replica
- Write: write data to main MySQL, and the other replicas will automatically sync. But only main mysql status will be acknowledge to the user.
- Read: cach of most recent users.
- Hot swap: once main is down, hot swap all the traffic to the replica.

Reason: can handle heavy read and heavy write.
Data: all other large information
Solution: Cassandra handle a heavy read and write. As the data grow bigger. We could maintain two kind of data: Live Viewing History and Compressed Viewing History.
- Live Viewing History: is the data being the most recently use. We support high speed read/write of those data.
- Compressed Viewing History: once some data are less likely being used recently. We could separate those data into another Cassandra node and compressed it to store.