A Standby in Another Availability Zone Is Insurance, and It Serves No Traffic at All
This node exists to prevent the specific confusion between a standby and a read replica, which the next two nodes depend on being resolved: one is a hidden synchronous copy that costs write latency and serves nothing, the other is a visible asynchronous copy that serves reads and is behind. It rests on the single-writer node and it is what the failover node acts upon. It also gives the recovery nodes their first honest number, since it is the mechanism that makes data loss from a hardware failure close to zero.
RDS Multi-AZ, Read Replicas, and Aurora in AWS
RDS Multi-AZ and read replicas are two independent, orthogonal mechanisms in relational database architecture that address different concerns: availability (automatic failover to a synchronously repl…