The CreateReplicationGroup action creates a replication group. A replication group is a collection of cache clusters, where one of the cache clusters is a read/write primary and the others are read-only replicas. Writes to the primary are automatically propagated to the replicas.
When you create a replication group, you must specify an existing cache cluster that is in the primary role. When the replication group has been successfully created, you can add one or more read replica replicas to it, up to a total of five read replicas.
This action is valid only for Redis.