Do you have some sources or experiences to share on this topic? I'm very curious. My experience is the complete opposite.
At my previous job there was a Java web application and running in Kubernetes (1 vCPU and 1Gi of memory) was able to deal with at most 80 requests per second, using up almost the full 1 vCPU and ~600-700MiB of memory. That was a bit disappointing, since we were supposed to support at most ~1000rps on this API, 13+ pods is a lot, and we felt "software could do better".
A reactive guru from another team told us we should use a reactive stack, so he came in and rebuilt the app using the reactive stack. Now it was doing about 120rps on one pod (about the same memory usage), which was a good improvement, but still disappointing.
One guy on the team was motivated to rewrite the API in Go as a proof of concept, and we were blown away. With the same 1 vCPU it was now able to handle 400 requests per second, while using ~100-200MiB of memory, and having approximately 20% better response times.
> builds just as fast (at least when not using some popular build tools)
I find this a little bit of a cop-out, because almost everyone is using the popular build tools. And it's quite a chore to build a full application without those popular build tools. With Go, all batteries for building are included.
