“The open source release is almost identical to our internal version. The only pieces swapped out are the toolchains (which point at the internal copies of our compilers) and remote execution (which points at our internal servers)”
Meta rewrote Buck from scratch in Rust and says builds now finish twice as fast as Buck1. The speed comes from remote execution and virtual file systems, the two pieces Meta swaps out for the public release. Meta runs millions of builds a day on its own servers. You get the same rules and your laptop.