Implementing API Versioning: Header-based vs URI-based

URI-based versioning (/v1/users) is discoverable and easy to cache; Header-based versioning (Accept: application/vnd.v2+json) is cleaner but harder to test and cache.

Senior architects must choose based on the 'Contract' longevity. URI versioning is standard for public APIs. Header-based versioning allows for 'Media Type' versioning, where the same URL returns different formats based on content negotiation.