Let's recap what we've learned in this chapter.

Current scaling demands are hard to meet using traditional approaches. The actor model with its shared nothing paradigm offers a solution to this problem. Akka is a library for building actor-based applications on the JVM. 

Actors communicate by sending and receiving messages and change their internal state and produce side-effects in response. Each actor has an address in the form of an ActorRef, which also encapsulates ab actor's mailbox and a dispatcher. Actors are organized into hierarchies where parent actors are responsible for the supervision of their children. 

Actors have a well-defined life cycle and implement a number of methods, which are called at appropriate moments during their lifetimes.

Akka provides additional modules that extend provided functionality even further.

We also looked at Akka FSM, which gives us the possibility to represent an actor as an FSM by encoding its possible states and state transitions.

Akka remoting implements the location transparency principle in practice and allows you to access remote Akka systems easily.

Testing actors is different from testing regular code. Akka TestKit is a library that's provided by the Akka team, which simplifies and streamlines the testing process. It does so by placing a tested actor in a controlled—but close to the real—environment.

In the next chapter, we will rebuild our bakery using different actor-based approach and different Akka library—Akka Typed.