If "customer says they are facing slowness" then my three first steps usually are
1) grep "ERROR:\|FATAL:" server.log
2) top. Maybe there is some unexpected process(es). Use a f, to sort by mem, cpu etc
3) query:
select datname, usename, client_addr, leader_pid, pid, DATE_TRUNC('second', query_start) query_start, wait_event_type, wait_event, query_id from pg_stat_activity where xact_start is not NULL order by 6;
and
\watch
And take a look at wait_event_type, wait_event
It gives glance, what is currently going on.
br
Kaido
