Redis
maang.io System Design Series
Redis is an in-memory data-structure server: not just a cache, but a toolbox of strings, hashes, lists, sets, sorted sets, streams, and more, served from RAM by a single-threaded event loop in sub-milliseconds. Add persistence (RDB/AOF), replication, and cluster sharding, and it becomes the swiss-army knife behind caches, rate limiters, leaderboards, queues, and session stores.
This deep dive comes in four parts:
- Foundations & Core Concepts — the data types and the single-threaded model.
- Internals — persistence (RDB/AOF), replication, and Redis Cluster hash slots, with worked numbers.
- Advanced Internals — eviction, pipelining, transactions, and Lua scripting.
- Interview — Staff/Principal Q&A: use-case fit, persistence trade-offs, and scaling.