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Sharded ElastiCache replication group needs a cluster mode review

AWS_OPS_062 MEDIUM Reliability

What it checks

Sharded ElastiCache replication group needs a cluster mode review

Where it applies

Terraform: aws_elasticache_replication_group

CloudFormation: AWS::ElastiCache::ReplicationGroup

How to fix it

  1. If the group does not already enable sharding, select a compatible parameter group with cluster-enabled set to true. For Terraform provider 5.x and later, review cluster_mode; in CloudFormation review ClusterMode. To move an existing disabled group to enabled, first use compatible, migrate clients, then enable. Do not add duplicate arguments to an already-enabled group.
  2. For Valkey or Redis OSS shard-count changes, review online resharding prerequisites and temporary performance impact. Terraform num_node_groups triggers resizing; CloudFormation requires UpdatePolicy UseOnlineResharding to avoid replacement. Review the deployment plan and backups rather than assuming a cache recreation is always needed.

Frameworks

These mappings are advisory, not an attestation of compliance.

Vendor documentation

All rules