Over the years Instagram (as a product) grew a lot. With more features to show, their web experience began to degrade. In a series of (upcoming) posts they’re covering what they have done to improve performance. In this first part they cover script preloading and image prefetching, reducing the loading time of the “feed page” by 50%.
Correctly prioritizing resource download and execution and reducing browser downtime during the page load is one of the main levers for improving web application performance. In our case, many of these types of optimizations proved to be more immediately impactful than code size reductions, which tended to be individually small and only began to add up after many incremental improvements.