Feature Flag Engineering Like a Pro: From JS Expressions to Global Rollouts

Build and Scale Feature Flags Like a Pro — No SaaS Required

Tired of bloated, expensive feature flag platforms? This in-depth guide shows you how to build a powerful, lightweight feature flag system using nothing but JavaScript. You'll learn how to evaluate flags at the edge, support percentage rollouts, run A/B tests, and manage flags across environments — all without third-party SDKs or vendor lock-in. Whether you're deploying on Cloudflare Workers, Vercel, or a Node backend, this is your blueprint for professional-grade, zero-dependency feature flags. Perfect for solo devs, startups, and teams that want full control and high performance.