Amazon ElastiCache
A managed in-memory cache that keeps hot data close so apps answer instantly.
ElastiCache is the AWS service that runs an in-memory data store for you, using the open source engines Valkey, Redis OSS or Memcached. Because the data lives in RAM instead of on disk, reading a value takes well under a millisecond. AWS handles the servers, patches, replicas and failover.
Its classic use is as a cache: a copy of answers that are expensive to compute or slow to fetch. Say the home page of a shop shows the 20 best-selling products, and building that list takes a heavy database query. The app runs the query once, stores the result in ElastiCache for a minute, and the next thousand visitors get it straight from memory. The database breathes, and pages load faster.
It is also used for things that need speed more than permanence: user sessions, rate limits, game leaderboards, short-lived counters. The trade-off is that memory is more expensive than disk and a cache can be emptied, so the real, durable copy of the data should still live in a database like Amazon RDS or Amazon DynamoDB.
Keep in mind
- Managed Valkey, Redis OSS or Memcached, run by AWS.
- Data in RAM means reads in microseconds, not milliseconds.
- Usually sits in front of a database to absorb repeated reads.
- A cache is a copy: the source of truth stays in the database.
