What is the Akka Framework?
What is an Actor in Akka?
The Actor System
Once again, notice that in Akka, the sole mechanism for inter-actor communication is message passing. Messages are the only thing that actors share and, since actors can potentially access the same messages concurrently, it is important for them to be immutable, in order to avoid race conditions and unexpected behaviors.
It is therefore common to pass messages in the form of case classes since they are immutable by default and because of how seamlessly they integrate with pattern matching.