Hi @schahaha,
Please note this is a bit simplified.
Akka actors run “on top” of a Thread Pool. This means code within the actors will be running on those threads.
Akka Actors process “one message at a time” so you don’t have to worry about locks. Of course one can run into some concurrency issues if modifying the actor’s internal state in the wrong place.
Regarding how Akka Actors achieve high concurrency, is all due to well tuned code underneath that produces a really low overhead. Why I think you can design highly concurrent systems with Akka Actors is because the Actor Model itself forces you to design and break your architecture in a more concurrent way.