Feature Flags: implementation and strategies

What are feature flags?

Feature flags (toggles) are switches that let you enable or disable functionality without deploying code. They enable gradual releases, production testing, and instant rollbacks.

Common strategies

• Release toggle: enables a feature for a percentage of users.
• Experiment toggle: used for A/B testing.
• Ops toggle: controls operational features (maintenance mode).
• Permission toggle: enables features based on user role.

Simple implementation

const featureFlags = {
  newCheckout: process.env.FLAG_NEW_CHECKOUT === 'true',
};

if (featureFlags.newCheckout) {
  return newCheckoutController(req, res);
}
return oldCheckoutController(req, res);

LaunchDarkly

Enterprise feature flag platform. Offers user targeting, segmentation, percentage rules, and audit trails.

Unleash

Open source alternative. Offers flags with strategies, user activation, gradual rollout, and WebHooks.

Best practices

• Temporary flags: remove them when the feature is stable.
• Descriptive and consistent names.
• Monitoring: usage metrics for each flag.
• Avoid nested flags (exponential complexity).

Want to implement feature flags? At Vynta we design gradual release strategies.