Elasticache is a web service that allows users to easily deploy, operate, and scale an in-memory cache in the cloud. It improves web application performance by using fast, managed Redis or Memcached caches instead of relying entirely on slower disk-based databases. Amazon Elasticache offers fully managed Redis and Memcached that can provide sub-millisecond response times for demanding applications. It allows users to seamlessly set up, run, and scale open-source compatible in-memory data stores in the cloud for uses like caching, sessions, gaming, geospatial services, analytics, and queuing.