You asked how it works, the post states how it works. You also asked if it's slow, which is clearly answered in the post (though you didn't quote that part). You also asked if there's some "secret sauce" allowing it to be fast, which is also a weird question since everything used is listed in the post.

If something wasn't clear to you, why not specifically ask about it? Even in this comment, you still don't specify what you don't understand. What kind of answer are you expecting to get?

You can Google the words you don't know, and find out that it does in fact answer your question.