Our platform uses some minimal per-environment configuration to determine on which tier it is running: dev, CI, QA, production. We have a fairly large number of application settings which vary by tier, such as data sources, ports and hostnames for external services, email addresses to be used for error reporting and so on. We also toggle features on and off in different environments so we can always have working builds for deployment to production (feature toggles allow us to develop and test features as t[...]