I thought Cloudflare was 100% Rust, and x86 (EPYC) these days.
Interesting to hear Go & ARM in use.
I doubt any company is mono language at that scale. Using ARM usually makes sense for s lot of horizontal scaling workloads so it's also not that surprising.
Cloudflare has long kept Arm builds of everything even when they deployed to x86 only, to make it easy to switch when it made sense.
And yeah, a lot of Rust but also a lot of Go.