Feature Flags - What and why

A feature flag (a.k.a. feature toggle) is a software development technique used to enable or disable certain functionality remotely without deploying code. Feature flags help decouple deployment from release letting one manage the full lifecycle of a feature.

Feature flag management allows for continuous integration/continuous delivery (CI/CD) to gradually roll out features to users. Continuous delivery enables shortening release cycles and getting new functionality in the user’s hands quickly and safely. Creating a CI/CD pipeline is necessary to increase the velocity of code deployments and thereby get software delivered to end-users faster. To move quickly, one needs safety measures in place - feature flags are one of those safety measures. With feature flags, one can turn off a feature that performs unexpectedly in production without rolling back the code.

Feature flags also eliminate the need to maintain multiple feature branches within the source code. All code changes can be made to the primary branch (trunk or master), and when the feature is ready it can be enabled via the flag. A single branch of code helps to eliminate merge conflicts, broken builds, thereby resulting in a cleaner codebase. Instead of using a feature branch, one can use a flag to gate features not ready for public viewing.

New features can be deployed without making them available to all users upfront. For example, a new feature can be made available to a small set of users for testing and feedback by using a feature flag to control this access.

Feature flags can also be used to manage beta programs, run A/B tests, and provision entitlements.

To sum up, feature management via flags is commonly used by enterprises looking at:

• Reducing the number of code rollbacks
• Gradual roll-out of new functionality to users
• Minimizing the risk of a release by first releasing to small groups of users
• User acceptance testing