Generate Redis cluster configurations with node types, replicas, and sharding.
Last verified: May 2026
Generate Redis cluster configurations with node types, replicas, and sharding.
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replicationGroupIdengineVersionnodeTypenumNodeGroupsreplicasPerNodeGroupOutput will appear here...The ElastiCache Redis Config Generator helps you build optimal Redis configuration parameters for Amazon ElastiCache. Redis has dozens of configuration parameters that affect memory management, persistence, eviction policies, and replication behavior. This tool provides guided configuration based on your use case (caching, session store, message queue) and cluster size, generating ElastiCache parameter group settings with explanations for each value.
A parameter group is a collection of Redis configuration values that you apply to your ElastiCache cluster. You cannot modify the default parameter group, so you create a custom one with your desired settings. Changes to some parameters require a reboot to take effect.
For general caching, allkeys-lru is usually best as it evicts the least recently used keys when memory is full. For caching with TTL-based expiration, volatile-lru only evicts keys with an expiration set. For session stores where you do not want eviction, use noeviction and ensure sufficient memory.
Your team's session store on ElastiCache started losing user sessions intermittently after traffic grew. Investigation reveals the cluster was on the default parameter group with maxmemory-policy=noeviction — Redis was REJECTING new session writes when full. The generator recommends a session-store parameter group with allkeys-lru eviction, longer maxmemory-samples (10) for better LRU accuracy, and notify-keyspace-events 'Ex' for session expiration tracking. Apply the new param group, reboot during low traffic, and session loss disappears.
The generator walks through your use case (cache, session store, queue, leaderboard) and recommends a parameter group with appropriate maxmemory-policy, eviction settings, persistence config, keyspace notifications, timeout values, and TCP keepalive. Output is generated as both an aws elasticache create-cache-parameter-group + modify-cache-parameter-group sequence and a Terraform aws_elasticache_parameter_group resource.
ElastiCache parameter changes split into two categories: dynamic (apply on next config refresh, no restart) and static (require a reboot). Always check which category your changes fall into BEFORE applying — accidentally toggling a static param can trigger an unplanned cluster reboot at 2pm on a Friday.
maxmemory-policy is the most-impactful single setting and the most-misunderstood. allkeys-lru is the right default for cache use cases. noeviction (the AWS default!) means writes will FAIL when memory is full instead of evicting old data — disastrous for caching. Always change from the default unless you're using Redis as a queue.
tcp-keepalive defaults to 300s on ElastiCache. For Lambda functions that hold a Redis connection across invocations, this can mean dead connections persist for 5 minutes. Lower to 60s for serverless workloads, leave at 300s for long-running app servers.
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