Most of the applications we use day to day have optimistic UI updates sprinkled throughout them if you look close enough. One familiar example we'll examine and use as an example throughout this course is liking and unliking a tweet on Twitter. In this video, we'll take a peek under the hood of https://twitter.com/ using Google Chrome's DevTools Network panel. We'll mimic a slow 3g network to slow things down and get a feel for exactly when the optimistic UI updates are occurring and when the UI state is reverted upon failure.