Mutex deadlocks in production: the patterns I found in my codebase and how I diagnosed them

Mutex deadlocks in production: the patterns I found in my codebase and how I diagnosed them It was 11:47 PM and the service wasn't responding. No panic. No error in the logs. Railway showed the container alive, memory stable, CPU at zero. Zero. That's what caught my attention: zero activity on a service that should've been processing queues. I opened a tokio-console session and there it was — four tasks suspended, all waiting on the same MutexGuard . None of them were ever going to move. That wa