How Facebook is bringing QUIC to billions

This post details Meta's development and deployment of QUIC and HTTP/3, replacing TCP and HTTP/2 for over 75% of their internet traffic. Key contributions include the development of the mvfst QUIC implementation, integration with Proxygen Mobile and Fizz, and strategies for deploying QUIC across Facebook and Instagram apps and web. The post highlights performance improvements (e.g., 6% reduction in request errors, 20% tail latency reduction for dynamic requests; up to 22% MTBR improvement for video) and challenges encountered, such as app logic heuristics tuned for TCP causing regressions, and the need to optimize mvfst's CPU efficiency and the BBR congestion control for static content. Solutions involved performance testing tools, pacing UDP packets, using GSO, optimizing data structures, and tuning flow control parameters. The deployment strategy involved phased rollouts, starting with internal traffic and then expanding to public-facing applications.