Postgres is a great pub/sub and job server (2019)
I know there used to be some O(n^2) logic associated with notify. Anyone know if that ever got fixed? Cursory search only turns up 
https://postgrespro.com/list/thread-id/2407396  The benchmark shows that the time to send notifications grows 
  quadratically with the number of notifications per transaction without 
  the patch while it grows linearly with the patch applied and 
  notification collapsing disabled.