All glossary terms
Cross-cutting
Dark launch
A dark launch ships a feature to production but leaves it disabled for users, the code runs (sometimes against real traffic, sometimes against shadow traffic) to validate behaviour under load before being turned on. Common pattern for high-risk database changes and traffic-heavy features.
Dark launching is the more disciplined cousin of feature flagging. Whereas a feature flag might gate a UI toggle, a dark launch runs the new code path against real production data and compares results (response time, error rate, output correctness) without affecting users. Amazon famously dark-launched the recommendations system: real production traffic, computing recommendations, not displaying them, for weeks, to validate accuracy before going live.