[jspthrowaway2]

Varnish isn't life-changing software. One thing Poul-Henning Kamp is very good at is selling Varnish, but once you use it for a bit you'll understand why it's a pretty advanced tool that many people avoid.

I've deployed Varnish once and I was annoyed by how it is configured. PHK will, of course, spin that as a positive, but my preference is not to write C when configuring my infrastructure support.

Beyond that, caching is a complicated topic with specific nuances for every deployment. As an example, I work on a high-traffic social site and we have absolutely no need for Varnish or any software like it. At its essence, Varnish is fixing a problem that many sites (a) do not have (yet), or (b) fix in other ways. We don't cache our dynamic views at all, and our system keeps up just fine. When it doesn't, we fix the system. Caching is on the radar as an improvement but we have determined that in terms of reward it does not make sense for our environment (invalidation is too frequent).

If you find yourself needing Varnish, ask yourself why. The answer to that question might lead you down some things to fix before investing in a big cache tier. There's a reason Facebook uses Varnish and you're wondering why others don't.