"The most simplest advise I would have is to have the ajax request trigger a background task and return immediately. The background task will then have some kind of side effect (ie. write some result to a database somewhere) which the ajax request can the look for with some kind of polling mechanism (on some other endpoint)." Wow, overkill much? Polling is bad, and is exactly the kind of bad solution that a lot of these libraries are in place to prevent developers from needing to do.

Websockets were made to solve the long-polling and poll-spamming that was prevalent. Now all you have to do is keep a light, open web-socket connection to the server. And the server, being async/evented, will respond when the task is good and ready. Nice and clean.