Redis + Messaging
20 min
Day 95: RabbitMQ: exchanges and routing
RabbitMQ: exchanges decide where a message goes
In RabbitMQ, a publisher never sends directly to a queue — it sends to an exchange, which routes the message to one or more bound queues based on the exchange type and a routing key.
- Direct exchange — routes to queues whose binding key exactly matches the message's routing key
- Fanout exchange — broadcasts to every bound queue, ignoring the routing key entirely
- Topic exchange — matches routing keys against wildcard patterns (e.g. "orders.*.created")
A topic exchange example
Routing key: orders.eu.created
Binding pattern: orders.*.created -> matches
Binding pattern: orders.eu.# -> matches
Binding pattern: orders.us.created -> does NOT matchWhy this indirection matters
Because publishers only know about the exchange, not the queues, you can add a new consumer (a new queue bound to the same exchange) without touching any publisher code — a real decoupling benefit, directly analogous to how a Kubernetes Service (Phase 9) decouples callers from specific Pod IPs.
Key terms
- Exchange
- Receives published messages and routes them to bound queues based on type and routing key.
- Topic exchange
- Routes messages using wildcard pattern matching against routing keys.
You need every subscribed service to receive a copy of every "user signed up" event, regardless of any routing key. Which exchange type fits?
