How would you implement 'default address' behavior in forms and APIs?

How would you implement 'default address' behavior in forms and APIs?

• A. Always assign a global default address for all users.
• B. Allow per-user/contact default, apply a system rule when not provided, and expose endpoints to set/update the default.
• C. Do not allow default addresses; require input every time.
• D. Use an external service to decide default automatically with no user control.

Answer: (B)

The main idea is to design a default address strategy that gives users control while also providing a sensible automatic fallback. Let users choose one address as their default for forms and APIs, so checkout, profile updates, and API payloads can automatically use that address. If a user hasn’t set a default, the system should apply a reasonable rule to pick one—such as the most recently used address or a predefined safe default—to keep flows smooth. Additionally, expose endpoints that let users (and admins) set or update the default address clearly, so the default behavior is transparent and auditable.

This approach is better because it combines user autonomy with predictable behavior. It avoids the rigidity of forcing a single global default for everyone, and it prevents the friction of requiring a value every time. It also keeps control out of an external service, which could introduce opacity and privacy concerns.