This chapter was all about building web apps on Heroku. With the help of a simple example, we learned the steps involved in building a web app. We also reviewed the guiding principles for developing SaaS web apps on the Heroku platform. We looked at the configuration API provided by Heroku CLI to set and unset environment variables for your app in the Heroku platform. We also delved a little deeper into buildpacks—Heroku's way of identifying the language runtime to be used for building your app. Finally, we looked at the process of slug compilation that builds your code into something executable, linking with it the necessary libraries and other assets.

Now that we have a reasonable understanding of Heroku's features, the platform stack, and the build process, it is a good time to learn how to run applications on Heroku; appropriately the subject of the next chapter.