Web performance: Cache efficiency exercise

What this post added

This post details a study conducted by Meta to measure the efficiency of browser caching for facebook.com, especially in light of their twice-daily release schedule. The study recreated a Yahoo performance research experiment by serving a special image with cache-controlling HTTP headers and logging requests. Results showed that 25.5% of requests were missing the cache, with significant variations across browsers (e.g., Firefox v32+ had skewed results due to a new cache backend). Analysis of cache duration revealed that for desktop users, 50% of requests had a cache that was at most 47 hours old. The findings suggest that while browser cache hit rates have improved since 2007, caches do not stay populated for long, a factor influenced by increasing webpage sizes and frequent code deployments. The post concludes that browser caching remains important and provides best practices for its utilization.