The Notes application stack

Did you notice earlier when we said run the Notes application stack? It's time to explain to the marketing team what's meant by that phrase. They'll perhaps need to put an architecture diagram on marketing brochures and the like. It's also useful for developers like 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 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 backend User Authentication Service over port 3333 (as currently configured).

In Chapter 10, Deploying Node.js Applications, we'll be expanding this picture a bit as we learn how to deploy...