Comment by cong-or

The 160k → 90k LOC reduction is nice, but the parallel rollout is the more interesting part. Running Rust alongside the C++ version and using differential fuzzing to check equivalence is a lot more realistic than “rewrite and pray.” You get incremental validation with the old system as a fallback. Curious how long they ran both before cutting over.

Binary size is a real concern on the client side. On servers the Rust stdlib overhead usually doesn’t matter, but when you’re shipping to billions of mobile devices, every KB counts. Good to see they invested in build tooling instead of just accepting the bloat.