I think one of the forgotten blessings of PHP/CGI was that requests had to finish sometime so as to free the PHP process for the next request. This alone I feel ended up making decisions easy around when it felt right to offload stuff when slow requests started to affect index.php from rendering in a timely fashion but now that's often masked (rightly) by caches and other tricks.

Right now in a microservice model often you have to remind developers that it just isn't ok to have a ~1ms response in a basic case and a 1 second to infinitely blocking case during errors or slow remote services.