We all know that the site loading speed depends a lot on Admin-ajax.php. Immaterial of the Heartbeat or any other setup we do on server side, it takes humongous time when loading on client side any how.

Also i read there is a solution to cache this Varnish config so as to help in reducing site load time.

This would be beneficial for all customers @ Cloudways as it would reduce there load time drastically.

https://guides.wp-bullet.com/how-to-cache-ajax-get-requests-with-varnish-4/

Also if you see in any clients Relic stats these ajax requests are on top of the list in consuming resources on the server side as well.

A small caching can make anyone's site load time below 2 sec. :)