Read replicas in RDS AWS

Question

My questions are:

1. For what kind of applications read replicas are suitable?
2. Is the read replica replicates synchronously or asynchronously data to other read replicas?
3. Is it the substitute for the Multi-AZ deployments?
4. Which is it better than the master-slave or master-master replication in MYSQL?
5. If we have replicas on EC2 will it work the same way as RDS read replicas work?

Answer 1

Read replica will be most suitable if your application is:

• Read intensive.
• Can live with a minor lag between the data written to DB and data replicated to read replicas.

Multi-AZ setup is for High Availability whereas Read Replica is purely to reduce the load on the Database Instances. This improves the read performance and avoids bottlenecks to the databases for writing and reading.

The comparison of the master-master vs master-slave depends on several factors like date, data volume, an operation like write or read, load, etc. you need to work to see exactly how the system performs with either of the setups.