If you render your content on multiple domains whilst editing your content via a sub domain then when it comes to a cache clear / purge it will get tricky sending all the purge urls to your proxy a

Varnish Tagged Cache Invalidation

This module provides a cache class exposing hooks allowing other code to intercept calls to the caching layer.

This module is a lightweight add-on to the CDN module which will rewrite the URLs of any images generated within a View.

Watchdog File Module

The Edgecast module connects your Drupal site to the CDN so that when you edit content the CDN knows to update it's cache quicker than the standard expiry time you've defined (usually hours or days