We use Varnish because it's configurable, and have 6-8x more app servers than cache servers. In the future we'll scale back the Varnish layer, since more and mo

We use Varnish because it's configurable, and have 6-8x more app servers than cache servers. In the future we'll scale back the Varnish layer, since more and more of what it does will be handled via CDN.