Rather than handling the multiprocessing and message passing yourself it would be much easier to use celery + gevent and let celery do the work of spinning up processes for executing the tasks.

It may feel limiting but my advice would be to keep all the celery job queue stuff isolated from your server, especially if you are using an async web framework. Have your web server just put all the jobs in the celery queue and let it handle executing them, regardless of whether they’re cpu or io-bound. If you try to optimize too much by doing something like leaning on celery for cpu-bound tasks but letting your web server handle the io-bound ones you’re going to be in for a world of hurt when it comes to both debugging and enforcing the order of execution. Celery has its warts but you’ll at least know where in the system your problem is and have reasonably good control over the pipeline.