For a long time, server-side development enjoyed a rich set of Toolkits for development, build and deployment. One of the most convenient features is the ability to externalize configuration from the actual source code. API URL, secrets, threshold limits etc can be configured outside the actual code and exposed via Operating system’s environment variables. This promotes a good practice of immutable build packages. These builds can be promoted without a need to make modification in the actual code to adapt to a changing environment.