Amazon ElastiCache

Cache service that reduces DB access and improves response time.

Amazon ElastiCache is a managed service that provides Redis-compatible or Memcached-compatible in-memory caching.

• Session management
• Caching DB query results
• Fast retrieval of leaderboards and temporary data

• In-memory cache service
• Choice between Redis-compatible and Memcached-compatible engines
• Used where low latency is required

• Reduces DB load on read-heavy systems
• Requires a fallback design for cache failures
• Used within a VPC

Amazon ElastiCache is a service that provides Redis-compatible or Memcached-compatible in-memory caches / in-memory data stores in a managed manner. Because it holds data in RAM and supports sub-millisecond read/write latency, it is used to offload high-frequency access to relational databases (RDS) and NoSQL databases (DynamoDB) onto a cache to reduce database load and response latency. Two engine families are available: Redis-compatible (based on Redis OSS / Valkey) and Memcached, to be selected according to the use case. The Redis-compatible engine provides rich data structures such as strings, hashes, lists, sets, sorted sets, and streams, as well as persistence (snapshot / AOF), replication, cluster configuration (sharding), pub/sub, and transactions. It is chosen for scenarios that require more complex data operations than a simple KV store, such as session management, ranking aggregation, messaging, and real-time leaderboards. The Memcached-compatible engine narrows the functionality to a simple KV cache but can deliver high throughput via multi-threading, making it suited for the use case of simply caching a large number of DB query results. The dichotomy is: choose the Redis-compatible engine when persistence or replication is needed, and choose Memcached for purely caching purposes that need to scale horizontally. Typical use cases in practice include session stores for stateless web applications, query result caches for SaaS applications where "the same user opens the same screen repeatedly", rankings / real-time aggregation, rate limit counters, and inter-component coordination via pub/sub. Place ElastiCache nodes inside a VPC and use Security Groups to permit traffic only from the connecting applications (EC2 / ECS / Lambda) so that they are not directly reachable from the internet. Because nodes incur per-hour charges while running, they tend to become a fixed-cost blind spot for personal-development MVPs, and it is often rational to defer adoption until requirements become clear. CLF-C02 asks questions such as "an in-memory caching service" and "a service that reduces DB access to speed up responses", while SAA-C03 and beyond ask in depth about Redis cluster mode, Multi-AZ replication, failover design, and how to differentiate ElastiCache from DAX (DynamoDB Accelerator).

• Amazon ElastiCache (AWS Official)
• What is Amazon ElastiCache (AWS Official Documentation)
• Selecting an Engine in ElastiCache (AWS Official Documentation)

Last updated: 2026-06-07