Feature Flags Hygiene

Feature flags hygiene

A feature flag lets you ship code dark and turn it on when ready, splitting deploy from release. The cost arrives later: every live flag doubles the paths the code can take, and forgotten flags compound until no one knows which branch runs in production. Treat each flag as debt with a due date.

Method

1. Name for intent and lifetime. Prefix by kind: release_, ops_, experiment_, perm_. release_checkout_v2 states its own purpose; flag_new_thing tells a maintainer nothing. Encode the owning team so an orphan has a contact.
2. Set an expiry at creation. Every release flag gets a removal date and a cleanup ticket in the same pull request that adds it. A flag with no death date becomes a permanent branch. Default release flags to 90 days.
3. Default to off, fail to off. New flags start disabled. If the flag service is unreachable, the code falls back to the old behavior, not to a half-shipped one. Test the off path, since it is what most users run.
4. Keep flag checks shallow. Read the flag once at the entry point and branch there, rather than threading if flag through ten functions. Deep checks are the ones stranded when you finally delete the flag.
5. Sweep on a cadence. Each sprint, list flags past expiry by crossing grep -rn "isEnabled(" src/ against the flag dashboard. For each, remove the flag and its dead branch, keeping the winning path.
6. Delete the flag and the loser together. Removing a flag means deleting the check, the config entry, and the code path that lost. A "cleaned up" flag that leaves dead else branches is half a job.

Checks

• Does every live flag have an owner, a purpose legible from its name, and an expiry date?
• Are any flags past their removal date still in the codebase?
• If the flag provider errored right now, would the app serve the safe old path?

Boundaries

Kill switches and long-lived operational toggles (ops_, perm_) are deliberately permanent: exempt them from expiry sweeps but still name and document them. Defer to your platform's flag tool (LaunchDarkly, Unleash, Flagsmith) for storage, targeting, and audit history.