Explanation
Why the waste happens and who it affects.
Valkey is a Redis-compatible, open-source engine supported by ElastiCache that may offer improved price-performance and licensing benefits. Valkey is designed as a drop-in replacement for Redis OSS 7, so most ElastiCache Redis OSS workloads can move to it, including those that use replication or persistence. Memcached, while simple, lacks key features like replication and persistence, and may be less cost-effective for certain access patterns. Choosing the wrong engine can result in overpaying for capabilities that aren't needed - or missing opportunities to optimize.
Billing model
The pricing dimensions that drive this cost.
ElastiCache is billed per instance-hour based on instance type and engine. Valkey is priced lower than the other engines (the pricing page cites 20% lower on node-based clusters and 33% lower on Serverless), and existing Redis OSS reserved nodes apply to Valkey nodes in the same instance family and Region. Performance and resource efficiency may also vary depending on workload and engine selection.
How to detect
4 checks to find it in your estate.
- Review the engine type for each ElastiCache cluster (Redis, Memcached, Valkey)
- Identify Redis OSS clusters, which are generally Valkey candidates even when they use features like persistence, pub/sub, or complex data types
- Evaluate whether Valkey would be a compatible and more efficient replacement
- Assess historical reasons for engine choice (e.g., legacy defaults vs. actual workload needs)
How to fix
4 ways to remove the waste.
- For Redis OSS workloads, consider migrating to Valkey
- If using Memcached, reevaluate whether Redis or Valkey offers better price-performance
- Redis OSS to Valkey can be done as an in-place cross-engine upgrade that keeps the same endpoint, with minimal downtime from Redis OSS 5.0.6 or higher; moving from Memcached requires a new cluster and data migration - plan accordingly
- Incorporate engine selection as part of architecture reviews for new cache deployments
Documentation
Vendor references for pricing and configuration.