Leader-based replication

All writes are directed through the leader, which propagates changes to the followers. Any follower can be used for reads. From the standpoint of external systems, the followers are read-only.

Leader-based replication can be implemented synchronously or asynchronously. Kleppman gives four implementation patterns for leader-based replication:

• Statement-based replication (251)
• Write-ahead log (WAL)-based replication (“physical log replication”)
• Logical (row-based) log replication
• Trigger-based replication