React and Progressive Web App (PWA) technologies have revolutionized the state of the art in web performance, enabling app-like speeds in the browser that would have been unimaginable a few years ago. Unfortunately, this kind of instant speed doesn’t come easy. In this talk, we’ll walk through the lessons for delivering the fastest possible website when wrangling these technologies. We’ll start by exploring common pitfalls in measuring and defining speed for modern sites, especially when measuring browsing speeds. Then we’ll cover techniques for improving real and user-perceived performance improvements, as well as the best process for migrating an existing site to a PWA. We’ll especially include techniques for dynamic, enterprise sites at scale, where traditional static and pre-rendering approaches don’t apply.