tl;dr:It takes 2x more time to write a patch if you are unfamiliar with the project, but 10x more time to figure out where to change the code. "ARCHITECTURE.md is a low-effort high-leverage way to bridge this gap." Aleksey gives us an example.
tl;dr:Although a Rust advocate, Aleksey argues the reasons not to use the language - you don't "ultimate performance" or control over hardware resources, it's complex, has a slow compile time, and more.