The read replicas feature is supported on SQL Server Enterprise Edition in the Multi-AZ configuration using Always On Availability Groups. This feature allows RDS SQL Server customers to offload their read workload from the primary DB instance to the replica, and also supports the scalability of read-heavy workloads over a farm of up to five read replicas. Read replicas can also render another level of availability by allowing you to promote a given read replica as a new standalone database, in the event of a failure of the primary DB instance.