[mbq]

According to the code, it actually does a file read on every request -- this is certainly suspicious because some implicit caching may significantly change the results.

[ww520]

It includes a test with file streaming on Node.js, that bypass reading the file and write to socket via the Javascript loop completely.

Also file IO are heavily cached by the OS. You can bet that one file is read from memory most of the time. Disk IO is pretty much out of the equation.