I'd just note that Rust isn't that hard to use for higher-level stuff. I am working on a network search engine (capture all traffic, index, search). At first I though I'd just write the capture agents in Rust, maybe some of the PCAP-storage stuff. Then write the entire query engine in F#. More and more, I'm realising I can write a much larger portion in Rust, and leave F# for the parts where performance totally doesn't matter (mainly interfacing with the end-user). It's pretty amazing.