> Transactional guarantees are hugely useful! Being able to rollback something like a user create including a queued job to send out a welcome email is incredibly nice.

That would work in this case - the job is added to the postgres table in a transaction, which eventually rolls back. The ID of the job was put into a separate queue. When the queue consumer tries to get the job from the database by ID, it doesn't see it because the transaction never committed. It can discard that job ID from its queue.