How would you version APIs for address management without breaking clients?

How would you version APIs for address management without breaking clients?

• A. Apply semantic versioning, maintain backward compatibility, deprecation timelines, and provide migration guides.
• B. Change the base URL for every new version without notices.
• C. Versioning is unnecessary if you have good tests.
• D. Always update the API in the client, not the server.

Answer: (A)

Versioning APIs without breaking clients hinges on treating the API as a contract that evolves in a predictable way. Semantic versioning communicates the nature of changes: patch releases fix bugs without changing behavior, minor releases add backward-compatible features, and major releases introduce breaking changes. By preserving backward compatibility in non-breaking updates, existing clients keep working while you introduce improvements. Deprecation timelines give developers advance notice about features that will be removed, creating a planned window to migrate. Migration guides then provide concrete steps to move from older versions to newer ones, making the transition smooth rather than abrupt.

The other approaches fall short because they either disrupt existing clients or ignore the contractual nature of the API. Changing the base URL for every version without clear notices causes immediate breakage. Relying on tests alone doesn’t protect clients from real-world contract breaks that occur in production. Updating the client without coordinating server changes is brittle and can leave the server and client out of sync. A thoughtful versioning strategy with clear compatibility rules and migration support is what allows the API to evolve safely while keeping existing integrations functional.