For some AJAX requests we doesn’t need the response (eg post view stats). You can add rules to make these requests run in background, so the browser won’t wait the response.
You can set background requests by request string key-value pair. For example if there is a request: https://yoursite.com/?action=post_view_count
you can set
action=post_view_count
Key-value pairs will work with POST and GET requests as well.