Early draft, please don't publish until the performance improvements are merged and shipped.
React 16.5 recently shipped, which added support for some new Profiling tools. We recently used these tools to identify a major source of slow render performance.
Faithlife.com is a web application powered by React 16.3. The homepage consists of a reverse-chronological timeline of posts. We received some reports that interactions with posts (such as replying) caused the browser to lag, depending on how far down the post was on the page. The further down the page the post was, the more lag occurred.
After updating React to 16.5 on a local copy of Faithlife, our next step was to start profiling and capture what components were re-rendering. Below is a screenshot of what the tools showed us clicking the 'Like' button on any post: