Explanation
Many workloads default to using Redis or Memcached without evaluating whether a lighter or more efficient engine would provide equivalent functionality at lower cost. Valkey is a Redis-compatible, open-source engine supported by ElastiCache that may offer improved price-performance and licensing benefits. For read-heavy or stateless workloads that don't require Redis-specific features (e.g., persistence, advanced replication), Valkey can often be used as a drop-in replacement. 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.
Relevant Billing Model
ElastiCache is billed per instance-hour based on instance type and engine. While pricing is nominally similar across engines, performance and resource efficiency may vary significantly depending on workload and engine selection.
Detection
- Review the engine type for each ElastiCache cluster (Redis, Memcached, Valkey)
- Identify Redis clusters that don't 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)
Remediation
- For Redis-compatible but non-persistent workloads, consider migrating to Valkey
- If using Memcached, reevaluate whether Redis or Valkey offers better price-performance
- Note that engine migration typically requires cluster recreation and data migration - plan accordingly
- Incorporate engine selection as part of architecture reviews for new cache deployments