I'm still surprised Facebook still has Facebook.com/somescript.php style links unless it's not as simple as it looks in the url. I know there's about 4 layers o

I'm still surprised Facebook still has Facebook.com/somescript.php style links unless it's not as simple as it looks in the url. I know there's about 4 layers of loadbalance/cache and layers of that in data centers but any idea about the framework or code design?