Feature Flag
A toggle in code that enables or disables a feature without redeploying. Lets you ship code to production behind a flag and turn it on for a percentage of users.
What is Feature Flag?
A toggle in code that enables or disables a feature without redeploying. Lets you ship code to production behind a flag and turn it on for a percentage of users.
Feature Flag is a intermediate-level concept that sits in the Microservices Architecture area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Feature Flag" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn Feature Flag in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Feature Flag lessonRelated lessons
Lessons that touch on Feature Flag as part of a larger topic.
Feature Flags for Resilience
Toggle features on and off without deployment, kill switches for problematic features
advanced · reliability resilience
Feature Flags
Deploying code to production without releasing features to users, decoupling deployment from release
intermediate · devops cicd
Graceful Degradation
Provide reduced functionality instead of complete failure, fallbacks, feature flags, and cached responses
advanced · reliability resilience
See also
Related glossary terms you might want to look up next.
Canary Deployment
Rolling out a new version to a small percentage of users first, then gradually increasing. Like sending a canary into a coal mine to test for danger.
Blue-Green Deployment
A deployment strategy using two identical environments. Traffic switches from blue (current) to green (new) instantly, with easy rollback.
CI/CD
Continuous Integration and Continuous Deployment: automating the process of testing and deploying code. Push code, tests run, and it ships to production automatically.