We can configure the service to use environment variables to change the behavior. For containers, this is a fantastic alternative to using configuration files, as it allows immutable containers that get their configuration injected. This is in line with the Twelve-Factor App (https://12factor.net/config) principles and allows for good separation between code and configuration, and the setting up of the different deploys that the code might be used for.
One of the advantages that we'll look at later with the use of Kubernetes is creating new environments on-demand, which can be tweaked for testing purposes or tailored for development or demo. Being able to quickly change all the configuration by injecting the proper environment makes this operation very easy and straightforward. It also allows you to enable or disable features, if properly configured...
