* Static assets. We set cache headers correctly; if you reload a bug, only the generated HTML is sent to the client. You can verify this with the network view in Firefox's Web Developer Tools or in Firebug.
* HTML layout. While old-school, the time to render the page in the browser is a very small fraction of the overall load time, much less than server-side generation and network transmission times. Again, this is verifiable with Firefox's Web Developer Tools.
* Hardware infrastructure. The webheads have ample processing power and memory.