Feature flag management and rollout strategy

Implement safe feature releases using feature flags. Flag types: 1. Release flags: control feature deployment (temporary). 2. Experiment flags: A/B testing (temporary). 3. Ops flags: circuit breakers for performance (permanent). 4. Permission flags: user role access (permanent). Rollout strategy: 1. Internal team (0.1% traffic): validate basic functionality. 2. Beta users (1% traffic): gather feedback from friendly customers. 3. Gradual rollout (5%, 25%, 50%, 100%): monitor metrics at each stage. 4. Success criteria: error rates <0.1%, performance impact <10ms, user feedback positive. Monitoring: set up alerts for error spikes, performance regression, customer complaints. Rollback plan: instant flag toggle if issues detected. Tools: LaunchDarkly, Split, Unleash, or custom solution. Flag hygiene: remove old flags after full rollout, document flag purpose and owner.