Separate configuration from application logic
Use the hosting platform’s supported configuration or secret mechanism for environment values. Keep nonsecret defaults in version control when appropriate, but do not commit credentials or rely on a developer’s local machine as the only source.
Define required keys and validate them at startup with clear, non-sensitive errors. Document which settings may differ across environments, such as service endpoints, feature flags, or resource identifiers.
Promote changes deliberately
Use the same release artifact where possible and inject environment-specific values at deployment. This reduces differences caused by rebuilding separately, while still allowing safe staging credentials and production endpoints.
Before promotion, compare configuration keys and verify that required integrations point to the intended environment. Record changes and provide a rollback path if a value is missing or misconfigured.