In Akka, message arguments have to be immutable objects - similarly for Erlang; Pony can pass isolated references which can be mutated and passed on, while stil

In Akka, message arguments have to be immutable objects - similarly for Erlang; Pony can pass isolated references which can be mutated and passed on, while still being data-race free. Scala is based on Java, and thus it is not data-race free - unless the program has been crafted very carefully.