Did you notice earlier when we said to run the Notes application stack? It's time to explain to the marketing team what's meant by that phrase. They may want to put an architecture diagram on marketing brochures or websites. It's also useful for developers such as us to take a step back and draw a picture of what we've created, or are planning to create.
Here's the sort of diagram that an engineer might draw to show the marketing team the system design (the marketing team will, of course, hire a graphics artist to clean it up):
The box labeled Notes Application in the preceding diagram is the public-facing code implemented by the templates and the router modules. As currently configured, it's visible from our laptop on port 3000. It can use one of several data storage services. It communicates with the User Authentication Service backend over port 5858 (or port 3333, as shown in the preceding diagram).
In Chapter 10,...