OK. I've read it a few times and still don't understand. Where is the distributed part? You store data in a single transaction into postgres. What/who is notifying the message queue?
Here's another blog post about how a Postgres-backed task queue can run at scale: https://www.dbos.dev/blog/making-postgres-queues-scale
When workers query the db for jobs the rows get locked by the select and there are no race conditions or duplicate assigned jobs