elasticache

name	elasticache
description	Manage Amazon ElastiCache clusters, replication groups, users, and snapshots for Redis and Memcached via AWS CLI.
metadata	{"openclaw":{"emoji":"⚡","requires":{"bins":["aws"]}}}

Amazon ElastiCache

Use this skill for in-memory caching and data store operations: creating and managing Redis and Memcached clusters, configuring replication groups, managing snapshots, scaling, and monitoring cache performance.

Prerequisites

• AWS CLI v2 configured with valid credentials
• IAM permissions: elasticache:* for full access, or scoped policies
• VPC with appropriate subnets and security groups (ElastiCache runs inside a VPC)
• redis-cli or memcached client for testing connectivity

Common Operations

List and Inspect (Read-Only)

# List all cache clusters
aws elasticache describe-cache-clusters --output table

# List clusters with detailed node info
aws elasticache describe-cache-clusters --show-cache-node-info \
  --query 'CacheClusters[*].[CacheClusterId,Engine,EngineVersion,CacheNodeType,NumCacheNodes,CacheClusterStatus]' \
  --output table

# Describe a specific cluster
aws elasticache describe-cache-clusters --cache-cluster-id <cluster-id> --show-cache-node-info

# List replication groups (Redis with replicas)
aws elasticache describe-replication-groups --output table

# Describe a replication group
aws elasticache describe-replication-groups --replication-group-id <group-id>

# List cache subnet groups
aws elasticache describe-cache-subnet-groups --output table

# List parameter groups
aws elasticache describe-cache-parameter-groups --output table

# List cache engine versions
aws elasticache describe-cache-engine-versions --engine redis --output table

# List snapshots
aws elasticache describe-snapshots --output table

# List users (Redis AUTH)
aws elasticache describe-users --output table

# List user groups
aws elasticache describe-user-groups --output table

# List reserved cache nodes
aws elasticache describe-reserved-cache-nodes --output table

# List events
aws elasticache describe-events --duration 1440 --output table

Create Clusters

⚠️ Cost note: ElastiCache pricing depends on node type. cache.t3.micro starts at $0.017/hr ($12/month). Production nodes (cache.r6g.large) are $0.18/hr ($130/month). Data transfer charges apply.

# Create a single-node Redis cluster (dev/test)
aws elasticache create-cache-cluster \
  --cache-cluster-id <cluster-id> \
  --engine redis \
  --cache-node-type cache.t3.micro \
  --num-cache-nodes 1 \
  --cache-subnet-group-name <subnet-group> \
  --security-group-ids <sg-id>

# Create a Memcached cluster
aws elasticache create-cache-cluster \
  --cache-cluster-id <cluster-id> \
  --engine memcached \
  --cache-node-type cache.t3.micro \
  --num-cache-nodes 2 \
  --cache-subnet-group-name <subnet-group> \
  --security-group-ids <sg-id>

# Create a Redis replication group (cluster mode disabled)
aws elasticache create-replication-group \
  --replication-group-id <group-id> \
  --replication-group-description "Production Redis" \
  --engine redis \
  --cache-node-type cache.r6g.large \
  --num-cache-clusters 3 \
  --automatic-failover-enabled \
  --multi-az-enabled \
  --cache-subnet-group-name <subnet-group> \
  --security-group-ids <sg-id> \
  --at-rest-encryption-enabled \
  --transit-encryption-enabled

# Create a Redis cluster (cluster mode enabled — sharded)
aws elasticache create-replication-group \
  --replication-group-id <group-id> \
  --replication-group-description "Sharded Redis" \
  --engine redis \
  --cache-node-type cache.r6g.large \
  --num-node-groups 3 \
  --replicas-per-node-group 2 \
  --automatic-failover-enabled \
  --cache-subnet-group-name <subnet-group> \
  --security-group-ids <sg-id> \
  --at-rest-encryption-enabled \
  --transit-encryption-enabled

# Create a cache subnet group
aws elasticache create-cache-subnet-group \
  --cache-subnet-group-name <group-name> \
  --cache-subnet-group-description "ElastiCache subnets" \
  --subnet-ids <subnet-1> <subnet-2> <subnet-3>

Modify and Scale

# Scale vertically (change node type) — requires replication group
aws elasticache modify-replication-group \
  --replication-group-id <group-id> \
  --cache-node-type cache.r6g.xlarge \
  --apply-immediately

# Add a read replica
aws elasticache increase-replica-count \
  --replication-group-id <group-id> \
  --new-replica-count 3 \
  --apply-immediately

# Scale out shards (cluster mode enabled)
aws elasticache modify-replication-group-shard-configuration \
  --replication-group-id <group-id> \
  --node-group-count 4 \
  --apply-immediately

# Modify cluster parameters
aws elasticache modify-cache-cluster \
  --cache-cluster-id <cluster-id> \
  --cache-parameter-group-name <param-group> \
  --apply-immediately

Snapshots

# Create a manual snapshot
aws elasticache create-snapshot \
  --replication-group-id <group-id> \
  --snapshot-name <snapshot-name>

# Copy a snapshot
aws elasticache copy-snapshot \
  --source-snapshot-name <source-snap> \
  --target-snapshot-name <target-snap>

# Export snapshot to S3
aws elasticache copy-snapshot \
  --source-snapshot-name <snapshot-name> \
  --target-snapshot-name <export-name> \
  --target-bucket <s3-bucket>

Delete / Destructive

🛑 DESTRUCTIVE — Always confirm with the user before executing any of these commands.

# Delete a cache cluster
aws elasticache delete-cache-cluster --cache-cluster-id <cluster-id>

# Delete with final snapshot
aws elasticache delete-cache-cluster \
  --cache-cluster-id <cluster-id> \
  --final-snapshot-identifier <snapshot-name>

# Delete a replication group
aws elasticache delete-replication-group --replication-group-id <group-id>

# Delete a replication group with snapshot
aws elasticache delete-replication-group \
  --replication-group-id <group-id> \
  --final-snapshot-identifier <snapshot-name>

# Delete a snapshot
aws elasticache delete-snapshot --snapshot-name <snapshot-name>

Safety Rules

1. NEVER delete clusters or replication groups without explicit user confirmation.
2. NEVER expose or log AWS credentials, Redis AUTH tokens, or passwords.
3. ALWAYS recommend creating a final snapshot before deleting clusters.
4. ALWAYS confirm the target cluster/region before write operations.
5. WARN about cost implications for larger node types and multi-AZ configurations.
6. WARN that --apply-immediately causes brief downtime for some modifications.

Best Practices

• Use replication groups with Multi-AZ and automatic failover for production.
• Enable at-rest encryption and in-transit encryption for sensitive data.
• Use Redis AUTH (user groups) to control access.
• Monitor with CloudWatch: CPUUtilization, EngineCPUUtilization, CurrConnections, Evictions.
• Use reserved nodes for predictable workloads to save 30-60%.

Common Patterns

Pattern: Production-Ready Redis Setup

# Create subnet group
aws elasticache create-cache-subnet-group \
  --cache-subnet-group-name prod-redis-subnets \
  --cache-subnet-group-description "Production Redis" \
  --subnet-ids subnet-aaa subnet-bbb subnet-ccc

# Create replication group with encryption and failover
aws elasticache create-replication-group \
  --replication-group-id prod-redis \
  --replication-group-description "Production Redis with HA" \
  --engine redis \
  --engine-version 7.0 \
  --cache-node-type cache.r6g.large \
  --num-cache-clusters 3 \
  --automatic-failover-enabled \
  --multi-az-enabled \
  --at-rest-encryption-enabled \
  --transit-encryption-enabled \
  --cache-subnet-group-name prod-redis-subnets \
  --security-group-ids sg-xxx \
  --snapshot-retention-limit 7

Pattern: Test Connectivity

# Get the endpoint
ENDPOINT=$(aws elasticache describe-replication-groups \
  --replication-group-id <group-id> \
  --query 'ReplicationGroups[0].NodeGroups[0].PrimaryEndpoint.Address' \
  --output text)

echo "Endpoint: $ENDPOINT"
# Then: redis-cli -h $ENDPOINT -p 6379

Troubleshooting

Error	Cause	Fix
CacheClusterNotFound	Cluster doesn't exist	Verify name/region with describe-cache-clusters
Connection timeout	Security group blocks access	Ensure SG allows port 6379 (Redis) or 11211 (Memcached)
InsufficientCacheClusterCapacity	Node type unavailable in AZ	Try a different node type or AZ
ReplicationGroupNotFoundFault	Replication group doesn't exist	Verify with describe-replication-groups
InvalidParameterCombination	Conflicting cluster-mode settings	Cluster mode enabled requires --num-node-groups instead of --num-cache-clusters
Evictions increasing	Memory pressure	Scale up node type or add shards