How can I reduce startup lag for video reels in my web app?

You might want to consider implementing a prefetching strategy. Many apps start loading the next several videos in the background to minimize loading times. This method often results in a smoother user experience because it preemptively fetches content before the user reaches it.

Double-check your setup to ensure that you are indeed fetching content through CloudFront rather than directly from S3. Using CloudFront can significantly improve streaming performance and speed. It’s also a good practice to incorporate prefetching for the next few videos to further enhance the experience, similar to how some popular apps do it.

Fetching directly from S3 can have geographic latency issues. If you're relying on AWS Amplify, CloudFront is typically set up automatically. Just ensure that all your S3 content is accessed via CloudFront to really take advantage of its caching capabilities. However, regardless of that, prefetching videos is still key to achieving a fluid playback experience for your users. Instagram uses a method that loads the first few seconds of the upcoming reels while the current one is still playing, which could be worth looking into for your app.