the only ones i know of for sure are the two script timers - in and out of combat have different values (in millliseconds) that addon code can run before its aborted and errors out.
there might be a saved variable memory allocation limit but i dont know for sure. i havent run into it.
for the timer theres a “multithreading” coroutine capability which lets you yield before hitting that timer value, the game does its thing for the next frame(s), then you need to re-call your code to start from where it left off (for another timer period).
so long as your code is written to survive being paused/restarted its a decent way around the timer, and stops the game from locking up (it just gets laggy instead)
the only way to know for sure would be for you to code it up and test that theory out.
that timer limit may also impact trying to process the data returned for a batch of 100 items whereas you may never need to worry about it when its only processing one item at a time.
most of the AH scan time would probably be from waiting for the server to return the data, and blizzard will just throttle that down even harder if people stress it out past what they think is too much.