Skip to content

SYSTEM Cited by 1 source

FL2

Definition

FL2 is Cloudflare's new Rust-based modular proxy that powers the edge request pipeline, replacing the older FL1 system built on NGINX with modules written in Lua. FL2's defining property is a strict module system that separates request-handling logic into well-defined, consistently ordered phases, where each phase statically declares its inputs and outputs. This lets the compiler surface broken interactions between phases when logic is reordered or moved — turning what would be risky pipeline surgery in FL1 into a compiler-checked, gradually-rollable change. (Source: sources/2026-08-14-cloudflare-secure-all-your-internal-vibe-coded-applications-in-one-click)

FL2 is described as "the new Rust-based modular proxy that powers Cloudflare's edge" and is the substrate on which products like Access and Workers run in a shared request pipeline.

Why it mattered: Access-on-Workers

Attaching Access to an individual Worker (instead of a hostname) required Access to know which Worker a request targets before it runs. That meant splitting Workers routing from Workers execution and moving routing to an earlier phase than Access in the pipeline.

  • In FL1 (NGINX + Lua), moving logic earlier is unsafe when it depends on shared state mutated by another product — interactions between products are subtle and hard to reason about.
  • In FL2, the phase-ordered module system makes inputs/outputs explicit and compiler-checked, so the reorder was safe to build and roll out gradually with confidence.

Seen in

Last updated · 766 distilled / 2,225 read