Redis

Redis is an in-memory data store used as a cache, session store, message broker, or low-latency database: strings, hashes, lists, sets, sorted sets, streams, and more with optional persistence and clustering. It sits beside primary databases like Postgres rather than replacing them for durable relational workloads. Deeper topics live in dedicated notes: data types, caching, streams, clustering, and the rest of the Redis cluster in the Backend MOC.