Cloudflare's Rust FL2 migration

Cloudflare said on April 17 that moving its core request-handling layer to a Rust-based system called FL2 made it the fastest network in 60% of the world’s top networks by December 2025. (blog.cloudflare.com) A content delivery network sits between a website and its visitors, routing requests to nearby servers so pages, images, and application data arrive faster. Cloudflare said FL2 now handles the layer where its security and performance products run after HTTP and Transport Layer Security traffic first lands on its edge. (blog.cloudflare.com) Cloudflare published the first detailed FL2 write-up in October 2025 and said the Rust rewrite cut median response time by 10 milliseconds, improved performance by 25%, and used less than half the central processing unit and memory of the older stack. The company said FL2 replaced a 15-year-old “FL” system built around NGINX, OpenResty and LuaJIT. (blog.cloudflare.com) The older FL layer had become one of Cloudflare’s last major NGINX deployments and could use 50 to 60 gibibytes of memory, according to a 2023 engineering post that described the system as hard to release and increasingly complex. Cloudflare said that earlier work split pieces out of FL before the full FL2 migration. (blog.cloudflare.com) Rust is a programming language designed to catch memory errors before software ships, which is one reason infrastructure companies use it for systems that process huge volumes of traffic. Cloudflare said Rust’s compile-time checks fit FL2’s modular design, where product modules have stricter input and output contracts. (blog.cloudflare.com) The migration also changed what hardware Cloudflare could use efficiently. In March 2026, the company said its new Gen 13 servers use 192-core AMD EPYC Turin 9965 processors, 768 gigabytes of DDR5-6400 memory, 24 terabytes of PCIe 5.0 NVMe storage and dual 100-gigabit Ethernet ports. (blog.cloudflare.com) Cloudflare said that pairing FL2 with those Gen 13 servers let it trade large cache memory for more compute cores and still avoid the latency penalty that hurt the older stack. The company said the result was 2x edge compute throughput and 50% better performance per watt than the prior generation. (blog.cloudflare.com) Cloudflare measured the 60% figure with real-user data and Transmission Control Protocol connection trimeans, a statistical midpoint measure that reduces the effect of outliers. In its previous performance update during Birthday Week 2025, the company had said it was the fastest network in 40% of the largest 1,000 networks. (blog.cloudflare.com) The immediate result is not a new product but a faster version of the layer that decides how Cloudflare applies security rules, routing logic and other services on nearly every request. After years of peeling old code away from FL, Cloudflare is now using the rewrite as the software base for its newest servers and its latest speed claims. (blog.cloudflare.com)