I have been following this thread with interest. Wouldn't Golang (over Erlang/Rust) be the ideal language here for scalable microservices ? Comes with in-built concurrency, all your afore-mentioned container orchestrators are written in Go-Lang and it comes with first class support for gRPC. Very stable, very easy to learn, a terrific concurrency model, great libraries for network programming, productive right off the bat and compiles to container-friendly binaries.