Redis
Redis, short for Remote Dictionary Server, is an open-source, in-memory data structure store used as a database, cache, and message broker. Created by Salvatore Sanfilippo in 2009, Redis supports data structures such as strings, hashes, lists, sets, sorted sets, bitmaps, and hyperloglogs. It is widely used for caching, session management, real-time analytics, and pub/sub messaging.
Varnish
Varnish, short for Varnish Cache, is a high-performance HTTP accelerator designed to speed up web applications by caching content in memory and reducing load on backend servers. Created by Per Bergström in 2006, Varnish is widely used in front of web servers such as Nginx and Apache HTTP Server to serve dynamic or static content with low latency.