The estimate is way off, when was the last time Vaccum was on the table?
about a week ago i ran this VACUUM VERBOSE ANALYZE;
this table is never updated or deleted, rows are just inserted...
You should analyze it more often, then... Postgres probably thinks the
table has the same data distribution as last week !
Analyze just takes a couple seconds...
Load on the database
how do i measure load on database?
Just look at vmstat.
Also if you very often do SELECT .. WHERE x = ... ORDER BY id DESC you'll
benefit from an index on (x,id) instead of just (x).