Build a Pub/Sub Broker

wildcard topics and consumer offsets

Challenge 3 of Async & MessagingIntermediate~55 min

Build the messaging backbone behind event-driven systems: callback subscriptions with clean unsubscribe, MQTT-style wildcard topic matching, retained messages so late subscribers catch up, an append-only log with offsets, and durable consumers that commit their position for at-least-once delivery.

5 steps

1. 1Subscribe and Publish
2. 2Wildcard Topics
3. 3Retained Messages
4. 4The Append-Only Log
5. 5Durable Consumers