What is Kill Switch?

A kill switch is a specific use of a feature flag designed to quickly turn off a feature when something goes wrong in production. Unlike regular feature flags used for releases, kill switches are kept permanently for critical features.

Kill switches provide a safety net for your most important functionality. If a new checkout flow starts throwing errors at 2 AM, an on-call engineer can flip the kill switch to revert to the old flow in seconds — no deployment, no code review, no downtime.

Best practice is to design kill switches as "default on" (the feature works unless explicitly disabled), and to wire them to monitoring alerts so that high error rates can automatically trigger the switch.