RabbitMQ vs MQTT
RabbitMQ and MQTT are not the same kind of thing, which is why this comparison confuses people. RabbitMQ is a message broker: a server that accepts, routes, and stores messages. MQTT is a wire protocol for publishing and subscribing over TCP, designed for constrained devices. RabbitMQ can speak MQTT through a plugin, so the real question is usually whether RabbitMQ is the right broker for an MQTT workload.
What RabbitMQ actually is
RabbitMQ is an open-source broker built around AMQP 0-9-1, with plugins for MQTT, STOMP, and WebSocket transports. Its distinguishing feature is routing. Publishers send to an exchange rather than to a queue, and the exchange decides which queues get a copy based on binding rules, so you can fan a message out to five consumers, route it by a header field, or send it to exactly one queue, all without changing the publisher. Queues are durable, deliveries are acknowledged individually, and unacknowledged messages are redelivered.
That machinery costs memory and operational attention. Each queue is a real object on the broker with its own state, and a RabbitMQ node handling hundreds of thousands of connections needs deliberate tuning. It is a good fit for service-to-service work in a data center and a mediocre one for a fleet of battery-powered sensors.
What MQTT actually is
MQTT is a protocol specification, not software. Its whole design goal is to move small messages over unreliable networks cheaply: a two-byte fixed header, topic-based publish and subscribe with wildcards, three quality-of-service levels, a keepalive so both sides notice a dead connection, and a last-will message the broker publishes on your behalf when a client vanishes. There is no exchange concept and no routing logic beyond topic matching.
Because MQTT is just a protocol, you still need a broker to run it. Mosquitto, EMQX, HiveMQ, and NanoMQ are purpose-built for it, and they hold far more concurrent connections per node than RabbitMQ will. If you are choosing between brokers rather than protocols, RabbitMQ vs Mosquitto is the closer comparison, and MQTT vs AMQP compares the two protocols directly.
Comparing the two
| RabbitMQ | MQTT | |
|---|---|---|
| Category | Broker software | Protocol specification |
| Native protocol | AMQP 0-9-1, plus MQTT via plugin | MQTT only |
| Routing | Exchanges, bindings, header and topic rules | Topic matching with wildcards |
| Acknowledgement | Per message, with redelivery | QoS 0, 1, or 2 |
| Typical client | Backend service | Sensor, phone, embedded device |
| Connection scale per node | Thousands | Hundreds of thousands |
Which one you should use
If your producers and consumers are backend services and you need routing, dead lettering, or per-message acknowledgement, run RabbitMQ over AMQP and ignore MQTT. If your clients are devices on flaky mobile or radio links, use MQTT, and pick a broker built for it unless you already operate RabbitMQ and the device count is modest, in which case the MQTT plugin saves you a second system to maintain.
Neither one solves the problem of notifying somebody else's server. Both expect a client that connects to your broker and holds the connection open, which you cannot ask of an external customer. That is what webhooks are for, and the two layers compose: consume internally over AMQP or MQTT, then deliver outward over HTTP. Svix handles the outbound side, including retries and signature verification. See webhook vs message queue for where the boundary sits.