I'm coming at it from the Ruby angle, in which jobs are often triggered using ActiveRecord after_commit hooks. I admit to being ignorant of the Python/Celery way of doing things so perhaps I am missing the point. I'm talking about jobs being produced atomically with the data that necessitated the background job (I realize not all background jobs are spawned in this fashion).

I agree with your point about polling being bad, however as someone pointed out below it's not an issue with Postgres's LISTEN/NOTIFY (and I added a note to the queue_classic gem which makes this easy to take advantage of in MRI Ruby).

Obviously I'm aware that Redis and RabbitMQ persist jobs. That's not what I was talking about at all.

I think we're on different wavelengths here so I'll let it be. :-)