Comment by ceeplusplus

It does look like with some GC tuning (e.g. manually triggering GC's at a smaller interval than the Go automatic GC threshold) they might've mitigated the spikes, although I don't think they would have gotten the level of perf improvement they did. Golang assembly code IME is not very optimized compared to Rust/C++.

edit: reading comprehension skills are lacking, please see comment below for why I'm wrong