I’ve never been able to articulate with specificity about my concern with using your database as your job queue, and I came across an article with concrete examples of how postgres can break down under queueing workloads:
https://richyen.com/postgres/2026/05/04/postgres_job_queue.html
There is nothing about ruby in this article, but I suspect (without verifying) it’s 100% applicable to rails database job queues.