#amqp

Data Engineering Bug Report

One RabbitMQ consumer hoarded 40,000 unacked messages while the others sat idle

Ravi Subramanian · Nov 9, 2026 · 7 min read

We scaled an image processing consumer from one to eight instances and the backlog barely moved. The first consumer had taken almost every message in the queue into its own buffer. Unlimited prefetch, early acks and how basic.qos and manual acknowledgements fixed the distribution.

Data Engineering Bug Report

RabbitMQ: a second service on the same queue silently took half the events

John Nguyen · May 7, 2026 · 8 min read

The analytics team started consuming our order events and fulfilment began missing about half of all new orders. Nothing errored. Both services were reading the same RabbitMQ queue, and a queue hands each message to exactly one consumer. We fixed it with an exchange and one queue per service.