Valkey is an open-source, BSD-licensed fork of Redis created in 2024 after Redis Ltd relicensed the Redis source from BSD to a dual SSPL/RSALv2 model that the Linux Foundation, AWS, Google Cloud, Oracle, and others judged unsuitable for open distribution. Valkey is now governed by the Linux Foundation and is API-compatible with Redis 7.2.

Why the fork happened

Redis was permissively licensed…

An in-memory database keeps its primary dataset in RAM rather than on disk, trading capacity and durability tradeoffs for orders-of-magnitude lower read and write latency. In-memory engines back almost every cache, session store, leaderboard, rate limiter, and many real-time analytics systems.

Common engines

• Redis. The dominant in-memory key-value store; rich data structures, optional…

An eviction policy is the rule a cache uses to decide which entry to remove when it reaches its memory limit and needs to make room for a new entry. Choice of policy directly affects hit rate and is one of the most consequential cache configuration decisions.

Common policies

• LRU (Least Recently Used). Evict the entry that has not been accessed for the longest time. Default in many systems;…

Redis (Remote Dictionary Server) is an in-memory data store that holds its dataset in RAM for sub-millisecond access. Beyond simple key-value, Redis supports rich data structures including strings, hashes, lists, sets, sorted sets, streams, bitmaps, and HyperLogLog.

How it works

A Redis server accepts commands over a simple text protocol (RESP). Commands are executed single-threaded, which…