Similar to how RDS is a managed Relation Database service. Elasticache is AWS’s managed cache service. Essentially how it works is Elasticache can cache user and database information for quick access. For example if a user makes a query to RDS that result is saved in Elasticache then the next time the user connects they are able to quickly retrieve that data from Elasticache rather than having to connect to the RDS instance. Another useful feature is the cacheing of user sessions. Let’s say for example a user connects to your RDS instance, that session is cached and if that same user attempts to access the application after only a short span of time they will not need to sign back in. Among Elasticache you have the offering of Redis and Memcached. Redis has multi-AZ, read replicas, as well as backup and restore features. Memcached doesn’t support these features however it does support sharding, spreading data across multiple instances in order to improve performance. Redis support IAM authentication and when you create your Redis cache you can set a password directly as well. Memcached utilizing SASL-based authentication. You can encrypt your Elasticache when you set it up. In Elasticache you have different patterns for Elasticache such as lazy loading, which caches all read data. Then there is write through which caches information when it is originally written to the DB. Elasticache is most useful for something like a leaderboard in a game, something that needs to be updated frequently and quickly.