A RabbitMQ Upgrade Exposed the Reliability Assumptions Hidden in Our Messaging System

Short summary

A RabbitMQ 3.X to 4.X upgrade exposed hidden reliability assumptions in connection lifecycle, acknowledgements, dead-letter routing, and queue declarations. The real lesson is that messaging code should be boring and understandable under pressure, not clever. Queue declarations should be treated like schema migrations with consistency, ownership, and migration thinking.

• •Upgrades test application assumptions, not just infrastructure
• •Messaging code should minimize operational surface area for incident response
• •Queue declarations are contracts with the broker and need migration-level discipline

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