I don't think that's correct - this would only happen if the notification queue was already full. Assuming the notification queue is not full then the original

I don't think that's correct - this would only happen if the notification queue was already full. Assuming the notification queue is not full then the original transaction does not wait for the notification to be ACKed. You can avoid most problems with listeners by having a single dedicated listener connection per application process (so all requests handled by that process multiplex onto the same listener). Since this connection only listens for notifications and never enters a transaction, it would be very difficult to fill up the notification queue. The queries themselves are executed on a separate connection pool, so that connections are never shared between the listener and other operations.