Redis

• Source: https://github.com/redis/redis
• License: BSD-3 (v7.2 and earlier) / RSALv2/SSPL (v7.4+)
• Alternatives: Valkey, Dragonfly, Memcached

In-memory database used for caching and message queuing.

To avoid network traffic/delays, run Redis on the same server as the containers that require it (one instance per server).

Features

• Sub-Millisecond Latency: In-memory storage for extremely fast reads and writes
• Rich Data Structures: Strings, hashes, lists, sets, sorted sets, streams, and more
• Pub/Sub Messaging: Broadcast events to multiple subscribers in real time
• Persistence: RDB snapshots and AOF append-only log for crash recovery
• Lua Scripting: Atomic server-side scripts for complex operations
• TTL & Eviction: Per-key expiry for cache use cases with configurable eviction policies