Backend
What is Pub/Sub (Publish–Subscribe)?
A messaging pattern where publishers emit events to topics and any number of subscribers receive them independently.
Definition
In the publish–subscribe pattern, senders publish messages to a named topic without knowing who will read them; subscribers register interest in topics and each receives a copy of every matching message. This differs from a work queue, where exactly one consumer handles each message. Kafka topics, Google Cloud Pub/Sub, Redis Pub/Sub, and NATS all implement the pattern with different durability guarantees. Pub/sub enables event-driven systems where adding a new consumer — analytics, auditing, cache invalidation — requires no change to the publisher.