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Pull requests are the beating heart of GitHub. As engineers, this is where we spend a good portion of our time. And at GitHub’s scale—where pull requests can range from tiny one-line fixes to changes spanning thousands of files and millions of lines—the pull request review experience has to stay fast and responsive. We recently shipped the new React-based experience for the Files changed tab (now the default experience for all users). One of our main goals was to ensure a more performant experience across the board, especially for large pull requests. That meant investing in, and consistently prioritizing, the hard problems like optimized rendering, interaction latency, and memory consumption.