This looks nice, I'll give it a try.
It's worth mentionning Huey too: https://huey.readthedocs.io/en/latest/ I've been using it for a year on top of sqlite.
I ran on Huey for a few years on a python/postgres ecosystem project fronted by Django, and ultimately migrated to django-postgres-queue, which is wonderful. (There has since been a fork that I have not used.) It uses the same underlying primitives as OP, and I would absolutely recommend this to anyone operating in the same ecosystem.