Feature Flag Service (TypeScript, Redis, PostgreSQL, React, Docker, Prometheus) overview

A self-hosted feature flag management service enabling progressive rollouts, A/B testing integration, and kill switches for production features. TypeScript powers the flag evaluation SDK and management API with type-safe flag definitions and targeting rules based on user attributes, percentages, and segments. Redis provides sub-millisecond flag evaluation with local caching and pub/sub-based cache invalidation across service instances. PostgreSQL stores flag configurations, audit trails, and targeting rule history. React delivers the management dashboard with flag lifecycle views, rollout progress charts, and approval workflows. Prometheus tracks flag evaluation latency and exposure counts for experiment analysis. Docker containers enable consistent deployment of the flag service alongside application pods. The tradeoff is managing flag lifecycle cleanup to prevent permanent flags and ensuring SDK performance under high evaluation volumes.