[ambiguity]

"Your only bottleneck in a web app should be: the databases, the workers. There are no excuses for the page generation to be slow. In the web speed is scalability because every web server is conceptually a parallel computation unit. So if the web page generation takes 10 ms instead of 100 ms I can server everything with just 10% of the hardware."

If the database is the bottleneck then the speed of web page matters much less. A page with a single 50 ms query will take %40 of the hardware (60 ms versus 150 ms).

This is even much less of an issue if you take into account how long it took for his test. PHP served 1500 requests per second vs Ruby's 250 requests per second which is equal to 0.7 ms per page and 4 ms per page. Assuming again you have a single 50 ms database query you are looking at 50.7 ms vs 54 ms which means you will need ~94% as much hardware. This is assuming that the database and webserver are on the same machine.

If one puts them on separate machines then the time of execution does not matter as long as the time it takes to query the database is less than the time it takes to render the page. Now this is bad in terms of page load as 50 ms + 49ms for page rendering is much more than 50 ms + 0.1 ms but in both cases you will be able to serve the same number of requests per second. This of course assumes that this is running in a multi threaded environment which allows one thread to sleep and other threads to start while waiting for a response from the database.