I believe the intention was more Zen -- don't write code that isn't really necessary -- and the "use standard libraries" code was separate. (If you are using a language where the standard libraries are so poorly implemented that you can easily write better versions, you might want to consider using a different language.)

I would also add the cargo cult suggestion of "precompute and cache everything you can". Whatever can be done in an indexing process instead of a search process should be; whatever doesn't need to happen at serving time shouldn't.