In nodeJS, I know that if I dump a bunch of big callbacks on some asynchronous calls, they'll all be put in the event loop and eventually resolved. I'm pretty sure, based on the MDN description of the event loop, that this is generally done in a FIFO manner.
On an application I'm working on, I dump a bunch of asynchronous calls that manipulate a database based on some web scraping requests every 30 minutes. I don't really care if these take a minute or two to get through, since I'm only calling them every 30 minutes and the volume of these calls won't change.
However, if a user makes a GET request to the server during that two minutes, I'd rather have them not hit lag while the server finishes up processing all of the web scraping. Is there a way to fast-track these user requests to the front of the event queue?
I think you have a misunderstanding here: it's not the asynchronous call that's being "put in the event loop and eventually resolved." Rather the asynchronous call works in the background (while other events such as your GET request are processed in the event loop) and when a result comes back, this result together with the callback is put into the event loop.
So the GET request that comes in is served immediately anyway and there should be no need to fast-track it.