Multi-AZ RDS

have an exact copy of your production DB

• in another AZ
• AWS handles the replication
• is case of failver -> standby instance
• only for disaster recovery

Read Replica

have an exact copy (read-only) of your production DB

• async replication from primary RDS to read replica
• only for read-heavy DB workloads
• used for scaling, not for disaster recovery
• up to 5 read replica copies for any DB
• each replica has its own DNS endpoint
• you can have read replicas that have Multi-AZ
• you can create read replicas of Multi-AZ source DBs
• you can have a read replica in a 2nd region