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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.

Go, Erlang, Elixer, Haskell, Clojure, Scala.