Hopefully, at this point, you have a good understanding of Akka HTTP and what you can do with it. You should know how the low-level server-side API leverages Akka Streams to support a back-pressure-aware HTTP server. You should also have a good understanding of how the high-level server-side API works on top of the low-level API, allowing you to build and compose complex route combinations with the routing DSL. If you need to consume those server-side RESTful APIs, then you know how to do so via Akka HTTP's outbound HTTP-handling API. This includes knowing which connection model to use for specific situations.

In the grand scheme of the bookstore refactor, this chapter may not have seemed very important in our plan to build a more scalable app. In reality, HTTP will be a very important concept in fully separating our service dependencies. It will allow us to go away from any tightly-coupled inter-module dependencies where we make direct actor calls across module boundaries. Instead...