I wrote a similar system for C# - we had three queues per application, work, delay, and error. In our system, the deferred queue used per-message TTLs that woul

I wrote a similar system for C# - we had three queues per application, work, delay, and error. In our system, the deferred queue used per-message TTLs that would push messages back onto the work queue. This allowed us to inspect the deferred and error queues while the application was running.