It was actually to do with docker rather than postgres itself. Docker limits shared memory to 64MB, and postgres died when it couldn’t allocate more. I saw this in the test server as well, but I didn’t want to assume so I waited to see it in production before applying the fix.
The error was something about failed to allocate disk space, the solution was to add shm_size: 1GB to the docker compose section for lemmy’s postgres.
I thought barometers were initially included to help with location. Air pressure isn’t just for weather, it also helps work out your altitude.