They claim "thousands of jobs every day", so the volume sounds very manageable. In a past job, I used postgres to handle millions of jobs/day without too much hassle.

They also say that some jobs take hours and that they use 'SELECT ... FOR UPDATE' row locks for the duration of the job being processed. That strongly implies a small volume to me, as you'd otherwise need many active connections (which are expensive in Postgres!) or some co-ordinator process that handles the locking for multiple rows using a single connection (but it sounds like their workers have direct connections).