Scalable but slow. CGI model of execution and everything being synchronous throws away too much effort that could have been shared between requests or spread ac

Scalable but slow. CGI model of execution and everything being synchronous throws away too much effort that could have been shared between requests or spread across CPU cores. Best case scenario, you have to tie your app in knots and come up with arcane cache keying/invalidation strategies to be able to cache exactly the right things, then you still have to make multiple round-trips to a cache service per page (unless every page is identical or every page is entirely unique), and PHP just twiddles its thumbs waiting on the network for each one, one after the other.