This doesn't improve anything because you're not actually cleaning the timer, just setting a boolean flag, so the callback is only going to run after the timeout expires anyway. And at that point making it conditional doesn't change anything since rejecting a resolved promise does nothing.

I don't think leaving the timers running in background is a huge problem since we'reunrefing them,queryTimeout is always small in practice, and you're going to have as many timers as there are queries one way or the other. That said, canceling them properly would be nice indeed and a marginal improvement.

What would be much more valuable IMO, is the opposite thing: cancelling the query execution when a timeout occurs instead of letting it hang in background. We could use anAbortController to send an abort signal to theQueryIntepreter, andQueryInterpreter could check ifAbortSignal is aborted before executing each step of the query plan, and throw the abort reason otherwise. We could even forward thisAbortSignal all the way to the driver adapters in case some database driver supports query cancellation.