“In practice, most of the apps I’ve worked on have fewer than a dozen background workers, and the cost is not likely to be significant.”
SKIP LOCKED gives you a job queue. Advisory locks give you distributed locking. LISTEN and NOTIFY give you pub/sub. Postgres has shipped all three for years, and teams still add Redis because a tutorial said to. Every extra service is another thing to patch, back up and page someone about at 3 a.m.