Feature Flag
A Feature Flag is a switch checked while software runs. It changes a feature without a new code deploy.
Another example
A new checkout reaches employees, then 5% of eligible shoppers. Error measures automatically trigger the documented off switch.
Main parts
- 01Identity or input
- 02Policy or transformation
- 03Stored result and audit evidence
Use it when
Use it for careful rollouts, experiments, or emergency shutdowns. Give every flag an owner and end date.
Do not use it when
Avoid permanent flags, hidden permission checks, untested combinations, and targeting based on sensitive traits.
Name used in code
flag key + targeting rule + default + expiry Before you ship
Check contracts and invariants, authorization, and input limits. Test retries, one-time effects, timeouts, and partial failures. Verify data integrity, compatibility, monitoring, recovery, and rollback.
Outcome: Design or review Feature Flag for this system while keeping data correct, secure, and easy to operate. User context: A new checkout reaches employees, then 5% of eligible shoppers. Error measures automatically trigger the documented off switch. Technical concept or control: Feature Flag. Why it fits: Use it for careful rollouts, experiments, or emergency shutdowns. Give every flag an owner and end date. Do not use it when: Avoid permanent flags, hidden permission checks, untested combinations, and targeting based on sensitive traits. Engineering requirements: Define inputs, outputs, contracts, and rules that must always hold. Set authorization and input checks. Define failures, timeouts, retries, one-time effects, data moves, and compatibility limits. Operations: Add useful signals and logs that hide sensitive data. Set capacity limits and write an operator guide. Test recovery and rollback. Acceptance criteria: Contract and failure-path tests pass. Data and authorization rules still hold during retries and partial failures. Check performance limits, monitoring, recovery, and rollback. Evidence and limits (evidence boundary): No single official standard controls the whole term. Its meaning may change across teams, platforms, or frameworks. Unknowns to confirm: Where the code runs, data stores, traffic shape, consistency needs, and the security boundary. Also confirm the compatibility period, service goals, and rollback limits.
Check this request
Review the current use of Feature Flag. Definition: A Feature Flag is a switch checked while software runs. It changes a feature without a new code deploy. Release checks: Check contracts and invariants, authorization, and input limits. Test retries, one-time effects, timeouts, and partial failures. Verify data integrity, compatibility, monitoring, recovery, and rollback. Before changing code, report the evidence you found, gaps, severity, and the smallest safe fix.