So does knowledge of your stack. Rails default settings are for development on one box, it expects you to look over the settings at least once before you push to prod. I can't blame Rails for not having "client demo for 20 people" as the default settings (and I also can't really blame GP for not thinking about Rails configuration too deeply as a junior engineer, that is on the more senior engineers on that team who apparently completely forgot to verify it worked before doing the demo).