Keeping settings out of code.
WHAT BELONGS OUTSIDE THE CODE
Credentials API keys Endpoints differing by environment Feature flags Anything differing between development and production
WHERE TO PUT IT
Environment variables, or a secrets service.
WHAT TO COMMIT
An example file listing every required value, without values.
WHAT NEVER TO COMMIT
Actual secrets.
WHAT TO DO IF ONE WAS COMMITTED
Rotate it, assuming compromise.
WHY
It remains in the history, and history is frequently public or widely accessible.
WHAT TO DO AT STARTUP
Validate that every required value is present, and fail immediately with a clear message if not.
WHY
Failing at startup is better than failing obscurely under load.
WHAT TO BE CAREFUL WITH
Secrets appearing in logs Secrets passed as command arguments, visible in process lists Configuration cached and not reloaded
WHAT TO ROTATE
Credentials, periodically and on any staff departure.
WHAT TO RESTRICT
Who can read production configuration.
WHAT TO RECORD
Where each secret lives and who owns it.
