Feature Flags & A/B Testing

Tactical patterns for flag evaluation, progressive rollouts, controlled experiments, and flag lifecycle — the code-level companion to infrastructure-level canary deployments.

When to Activate

• Adding feature flag support to a new or existing service
• Designing a percentage-based or ring-based rollout
• Setting up A/B experiments or multivariate tests
• Choosing between LaunchDarkly, Unleash, and OpenFeature
• Implementing sticky bucketing or mutual exclusion across experiments
• Writing unit or integration tests for flag-gated code paths
• Auditing, cleaning up, or governing stale flags

Flag Types & Evaluation Context

Four flag types cover all use cases: