In the first part of the presentation we see how Symfony2 implements HTTP cache. In the second one there's an explanation of why application cache layers suck, why nerly every php application does caching in the less productive way and how you benefit from HTTP cache from this point of view.
![Be lazy, be ESI: HTTP caching and Symfony2 @ PHPDay 2011 05-13-2011](https://cdn-ak-scissors.b.st-hatena.com/image/square/f206821142a1be391be751f2fb0adb0ae692a3f3/height=288;version=1;width=512/https%3A%2F%2Fcdn.slidesharecdn.com%2Fss_thumbnails%2Fbelazybeesiphpday2011-110513110805-phpapp01-thumbnail.jpg%3Fwidth%3D640%26height%3D640%26fit%3Dbounds)