Performance at GitHub: deferring stats with rack.after_reply | The GitHub Blog

How we sped up GitHub.com by moving slow, non-critical code into rack.after_reply.Performance is an essential aspect of any production application, and GitHub is no exception. In the last year, we’ve been making significant investments to improve the performance of some of our most critical workflows. There’s a lot to share, but today we’re going to focus on a little-known feature of some Rack-powered web servers called rack.after_reply that saved us 30ms p50 and 50ms p99 on every request across the site.