Interestingly, when a place does get to the point where the single instance has capacity issues (after upgrading to EPYC and lots of flash drives) then other non-obvious stuff shows up too.

For example, at one place just over a year ago they were well into this territory. One of weird problems for them was with pgBadger's memory usage (https://github.com/darold/pgbadger). That's written in perl, which doesn't seem to do garbage collection well. So even on a reporting node with a few hundred GB's of ram, it could take more than 24 hours to do a "monthly" reporting run to analyse PG usage for the time period.

There wasn't a solution in place at the time I left, so they're probably still having the issue... ;)