Feature Flags That Actually Ship: Lessons From the Trenches

It was 2:47 AM when the alerts started. A seemingly straightforward database migration had triggered a cascading failure across three downstream services, and our payment processing pipeline was dropping roughly 12% of transactions. The on-call engineer didn't need to wake anyone, locate a rollback script, or wait for a CI pipeline to churn through another deploy. She opened the LaunchDarkly dashboard, toggled one kill switch, and the system reverted to the stable path within seconds. The migrat