Most tutorials teach you how to build a button. This post teaches you why the browser renders that button, what happens when a user clicks it on a phone with a 3G connection, and why your rendering strategy choice can make or break a business. Frontend engineering is not the "easy" side of software. It's the side where every millisecond of latency is felt by a real human being, where you ship code that runs on hardware you don't control — thousands of device models, dozens of browser versions, n