Part 3

Redis and Caching

In-memory data structures, caching patterns and their failure modes, memory and eviction, persistence, replication, Sentinel, Cluster, pub/sub, and distributed locks.

Redis is the Swiss-army knife of the stateful tier: cache, session store, rate limiter, leaderboard, queue, and lock service, all in memory at sub-millisecond latency. It's simple to start and easy to misuse: most Redis outages come from treating a cache as a database, running out of memory, or one slow command blocking everything. (Valkey, the Linux Foundation fork used by ElastiCache and many distros, behaves the same for everything in this part.)

1. 3.1

   Data Structures and Caching Patterns

   Beginner

   Redis's core types and what each is for, TTLs, cache-aside vs write-through, invalidation, cache stampedes, and sessions and rate limiting in Redis.

   45 min · 4 lab steps · 2 drills

2. 3.2

   Memory, Eviction, Persistence, and Slow Commands

   Intermediate

   maxmemory and eviction policies, big keys and hot keys, RDB snapshots vs AOF, fork and copy-on-write, the SLOWLOG, and the commands you should never run in production.

   45 min · 4 lab steps · 2 drills

3. 3.3

   Replication, Sentinel, Cluster, Pub/Sub, and Distributed Locks

   Advanced

   Async replication and its data-loss window, Sentinel failover, Redis Cluster hash slots and MOVED redirects, hash tags, pub/sub vs streams, and how (not) to build a distributed lock.

   55 min · 4 lab steps · 2 drills