Feature Flags, A/B Testing, and Releases

Feature flags and A/B testing are cornerstones of modern React development. They let you ship code without shipping features, run experiments on live users, and roll back instantly if something breaks—all without redeployment. This series covers building a production-grade feature-flag system, running statistically rigorous A/B tests, implementing canary and blue-green deployments, and using kill switches to protect your app when things go sideways.

Whether you're a startup scaling fast or an enterprise managing thousands of concurrent experiments, the patterns you'll learn here will transform how you think about releases. You'll move away from the all-or-nothing binary of "live in production" vs. "not live" and toward a more granular, data-driven approach: deploy to 1% of users, measure impact, and expand if safe. By the end, you'll understand how LaunchDarkly, Statsig, and open-source libraries like Unleash or feature-flag-js integrate into React, how to instrument tracking so your experiments are statistically valid, and how to analyze results to drive product decisions backed by data.

This series assumes you know React hooks, async data fetching, and have deployed to production at least once. You don't need DevOps expertise—we'll explain infrastructure concepts as we go. Each article is self-contained but builds on the previous one; start with the fundamentals and progress to advanced release strategies.

Articles in this series​

Articles in this series