I mean, ideally there should be absolutely no bearing of usage of ORM on the snappiness of UIs. It should absolutely never block the Ui thread. At most it could add longer “in progress” screens or something, but that is a different topic (also, good ORMs when used correctly, that is the developer actually knows what he/she does and not only blindly copies code, than I doubt they would cause serious overhead. But I agree that non-correct usage can cause problems)