Question 1

What's the difference between a feature flag and a canary release?

Accepted Answer

A feature flag is a switch in your application that turns a feature on or off at runtime (often per user, per region, or per percentage). A canary release is a deployment strategy where you ship a new version to a small portion of traffic first. They’re often used together: you can deploy code everywhere, then use a feature flag to expose it to a small audience and expand gradually.

Question 2

When should I use feature flags?

Accepted Answer

Use feature flags when you want safer releases and more control over who sees a change. Common cases include gradual rollouts, A/B testing, separating deployment from release (deploy now, enable later), quickly disabling a problematic feature without a redeploy, and running experiments for specific user segments. Avoid using them as permanent branching logic—plan to remove flags after the rollout is complete.

Question 3

How much do feature flags cost?

Accepted Answer

Cost depends on how you implement them. Third-party feature-flag platforms typically charge by seats, monthly active users, requests/evaluations, environments, and advanced capabilities (experimentation, approvals, audit logs). A self-managed approach can be low direct cost but requires engineering time and infrastructure (a config store or database, caching, high availability, monitoring, and security). Also consider indirect costs: operational overhead, performance impact of flag checks, and the need to clean up old flags.

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