Comment by mianos
5 years ago
Skype at its peak used a postgres queue extension, pgqueue, at its core. Seemed to go OK for them. The extension did work around some limitations when running a pure sql queue in postgres. These days I would run Pulsar but if you only have a million users and already have postgres you will be fine.
I worked at a place using pg_queue (the person who created it worked there before going to Skype IIRC) and maybe it was working well operationally but it was not a great experience to develop on it. It was hard to generate events and debug/observe them (it was height years ago so the details are a bit fuzzy).
MS also moved from it afterwards when they acquired Skype but I guess it was more because of the shift to SQL Server.
Marko Kreen? He still maintains it so I guess some people still use it and the associated logical table distribution system.