Here is a weird thing, the following query takes too long SELECT P.name FROM People P WHERE P.nick = P.name AND (SELECT flow FROM Traffic T WHERE T.name = P.name AND T.checkDate="2020-06-25") >= 500 while if I remove the "checkDate" constraint, it gives me 1300 records instantly. Is the query not being optimized in the first case ? BTW I have indexes on all the mentioned fields !