Well my question to you is, where is this application living? Is not the DATABASE_URL an environment variable? If so, then in a Kubenetes cluster, you could have different deployments that populate that variable according to where the application is living. So when you app lives in DEV, CERT, or PROD, whatever your config is set up, there, your value will be tied back to DATABASE_URL because of the injection that happens via Kubenetes into the container.