Redis Pub/Sub
maang.io System Design Series
Redis Pub/Sub offers dead-simple channel messaging: subscribers listen, publishers send, and Redis fans out instantly. The catch is it's fire-and-forget with no persistence — a disconnected subscriber misses messages (at-most-once). Knowing exactly where that's fine (live notifications, chat, cache invalidation) and where you need Redis Streams or Kafka instead is the whole lesson.
This deep dive comes in three parts:
- Foundations & Core Concepts — channels, pattern subscriptions, and fire-and-forget delivery.
- Internals — sharded pub/sub, and Redis Pub/Sub vs Streams vs Kafka, with worked examples.
- Interview — Staff/Principal Q&A: its hard limits and when to reach for a durable log.