Thanks for noticing the speed :) I spent a lot of effort on that.

I built my own mini-framework for Google App Engine with a focus on speed. The main thing that makes it fast is that it utilizes public edge caching for most content, and the parts of the content that change from user to user are updated with javascript.

So with the home page, App Engine just serves a static page from it's edge cache, which is updated every 30 seconds, and the top bar of the site which is different if you are logged in is updated with javascript to show you different links if you are logged in.