Cache overview

In-memory key/value store providing sub-millisecond reads for frequently accessed data, reducing load on the primary database and improving response latency. Caching strategies include cache-aside, read-through, write-through, and write-behind patterns. Redis (the dominant choice) supports rich data structures (hashes, sorted sets, streams), pub/sub, Lua scripting, and optional persistence via RDB and AOF. Memcached is simpler but faster for pure caching. Varnish operates at the HTTP layer for full-page or fragment caching. Key operational concerns include cache invalidation strategies, TTL tuning, eviction policies (LRU, LFU), and hot-key management in clustered setups.