I am the author of the major web frameworks for ocaml [0]. On of the nicest things about OCaml is the identical system calls. I built my entire OWebl platform by reading through C servers.
On the other hand, Rust (like Erlang) reinvents and wraps a lot of these calls in ways that are not immediately obvious. (Or at least, not AS immediately obvious as they are in OCaml.)
This is such a tremendous aid because there are nearly limitless documents and examples of the Unix API.