Lesson 18 / 18

Redis as a Message Broker

Q: Does plain Redis Pub/Sub store messages for subscribers who are offline?

No — only currently connected subscribers get it. Pub/Sub has no storage — use Redis Streams when messages need to survive for offline consumers.

Pub/Sub vs Streams, and where Redis fits among message brokers.

Pub/Sub is fire-and-forget

Plain Pub/Sub delivers messages only to subscribers connected right now — nothing is stored, so an offline consumer misses it forever. Redis Streams (XADD/XREAD) add a durable, replayable log for when messages must not be lost.

Not a Kafka replacement

For lightweight, low-latency messaging Redis is excellent; for massive, guaranteed-durable, multi-day event streams, a dedicated broker like Kafka or RabbitMQ is usually a better fit.

Quick check: Does plain Redis Pub/Sub store messages for subscribers who are offline?

Yes, forever
No — only currently connected subscribers get it
Yes, but only for 24 hours

Answer

No — only currently connected subscribers get it — Pub/Sub has no storage — use Redis Streams when messages need to survive for offline consumers.