Thomas Carroll <tomfecarroll@yahoo.com> writes:
> Postgres version: 10.5. work_mem setting: 4MB, shared_buffers setting: 800 MB, connections typically around 30-40.
I imagine you checked this already, but ... what is temp_buffers set to?
That constrains the maximum memory used for temporary-table buffers in
each process, and an unreasonable setting for it could lead to the
described behavior.
Another thing to keep in mind with long-lived "temporary" tables is
that autovacuum can't do anything with them; so it's incumbent on your
application to periodically VACUUM and/or ANALYZE them as needed.
Otherwise such tables will bloat, which could contribute to excessive
use of temporary-table buffers.
regards, tom lane