Integration / RabbitMQ Interview Questions
Why doesn't RabbitMQ guarantee message ordering in all cases?
RabbitMQ preserves strict FIFO order only within a single queue, delivered to a single consumer, and even then only under specific conditions - several common setups break that guarantee.
- Multiple consumers on one queue - messages are dispatched round-robin, so consumer A and consumer B may finish processing in a different order than the messages were enqueued.
- Requeued/redelivered messages - a nacked message often goes back to a different position, interleaving with newer arrivals rather than resuming its original spot.
- Priority queues - by design, higher-priority messages jump ahead of lower-priority ones already waiting.
- Sharding across multiple queues (e.g. via a consistent-hash exchange) - order is only preserved within a shard, not globally.
If strict ordering is a hard requirement, the usual approach is a single queue with a single consumer for that ordering domain, accepting the throughput ceiling that comes with it.
Which setup is most likely to break FIFO ordering?
Why do priority queues break strict FIFO order?
More Related questions...
