Amazon ElastiCache for Redis
ElastiCache for Redis User Guide (API Version 2015-02-02)

Adding a Read Replica, for Redis (cluster mode disabled) Replication Groups

Information in the following topic applies to Redis (cluster mode disabled) replication groups only.

As your read traffic increases, you might want to spread those reads across more nodes and reduce the read pressure on any one node. In this topic, you can find how to add a read replica to a Redis (cluster mode disabled) cluster.

A Redis (cluster mode disabled) replication group can have a maximum of five read replicas. If you attempt to add a read replica to a replication group that already has five read replicas, the operation fails.

For information about adding replicas to a Redis (cluster mode enabled) replication group, see the following:

You can add a read replica to a Redis (cluster mode disabled) cluster using the ElastiCache Console, the AWS CLI, or the ElastiCache API.

Adding a Read Replica to a Replication Group (AWS CLI)

To add a read replica to a Redis (cluster mode disabled) replication group, use the AWS CLI create-cache-cluster command, with the parameter --replication-group-id to specify which replication group to add the cluster (node) to.

The following example creates the cluster my-read replica and adds it to the replication group my-replication-group. The node types, parameter groups, security groups, maintenance window, and other settings for the read replica are the same as for the other nodes in my-replication-group.

For Linux, macOS, or Unix:

aws elasticache create-cache-cluster \ --cache-cluster-id my-read replica \ --replication-group-id my-replication-group

For Windows:

aws elasticache create-cache-cluster ^ --cache-cluster-id my-read replica ^ --replication-group-id my-replication-group

For more information on adding a read replica using the CLI, see create-cache-cluster in the Amazon ElastiCache Command Line Reference.

Adding a Read Replica to a Replication Group Using the API

To add a read replica to a Redis (cluster mode disabled) replication group, use the ElastiCache CreateCacheCluster operation, with the parameter ReplicationGroupId to specify which replication group to add the cluster (node) to.

The following example creates the cluster myReadReplica and adds it to the replication group myReplicationGroup. The node types, parameter groups, security groups, maintenance window, and other settings for the read replica are the same as for the other nodes myReplicationGroup.

https://elasticache.us-west-2.amazonaws.com/ ?Action=CreateCacheCluster &CacheClusterId=myReadReplica &ReplicationGroupId=myReplicationGroup &Version=2015-02-02 &SignatureVersion=4 &SignatureMethod=HmacSHA256 &Timestamp=20150202T192317Z &X-Amz-Credential=<credential>

For more information on adding a read replica using the API, see CreateCacheCluster in the Amazon ElastiCache API Reference.