When the company rapidly grows you get mysterious bugs - in the worst case customers seing other customers data because of the wrong transaction levels.
through that:
> in the worst case customers seing other customers data because of the wrong transaction levels.
should not happen even with wrong transaction levels, that indicates some additional serious design problems IMHO, likely related to premature optimizations
From my understanding getting this kind of error would involve something going wrong at a pretty low level? I am not sure how a developer could cause this at the ORM level.
You can't effectively use an ORM without detailed knowledge of the generated output unfortunately. It does not add locks for you, so it's probably just wrong in prod when horizontally scaled and requests span multiple statements.
I don’t recall ever having a transaction isolation issue with my busy stored procedures - though I often use SELECT .. FOR UPDATE which is maybe cheating because an ORM can’t do that efficiently - but I’ve certainly seen them in ORMs.