It was never on my radar. I'll search around for some resources about it. Thanks.

Site is open sourced, feel free to send PR with missing things - https://github.com/strzalek/queues.io

Celery is more of a distributed processing framework than a queue in and of itself. It usually plugs into a queueing system, but you can have it use mongo or redis for it's backend if you want and no one would call those queueing systems.