Any language that uses the actor model for concurrency which is basically every language created in the last decade. Elixir, GO, Akka framework for Java and C#, Pony, Dart, Erlang, ELM, SCALA, ...
F# with it's built in actor model, robust OCaml based syntax, great support for functional Akka[.net] actors, simplified concurrency and asynch programming support, and very own ELM implementation is a great contextual answer for anyone who wants to be on the front lines of lightweight non-blocking concurrent & parallel web development in .Net land.
C# is fairly efficient while still having managed memory. And, of course, golang was designed to hit the sweet spot of automatic memory management, decent performance, and non-blocking I/O.
Beyond that, there's things like Erlang and Elixer, which I am less familiar with. My understanding is that the Erlang VM is significantly slower than JVM or CLR implementations but generally faster than scripting language runtimes.
