Postgres PubSub is great for triggering job dispatch, but it isn’t good enough on its own. There are a few caveats that make polling an additional requirement:

1. Message compaction — notifications are deduplicated, so if two jobs are inserted in the same queue the system may only get one notification. 2. Message saturation — with high levels of activity you’ll need to start discarding messages, essentially denouncing, otherwise the database gets throttled. 3. Dedicated connections — pubsub requires a dedicated connection for listening, which requires a single connection with custom dispatching or one connection per queue.

Relying on PG for everything is awesome regardless!