API Surface Evolution

Design for change without breaking clients.

Versioning Strategy

• Choose explicit versioning (URI /v1/... or header negotiation)

• Default to additive changes; never break a released contract

DTOs & Transformers

• Define versioned DTOs; map from models/services via transformers

• Keep controller thin—validate → transform → respond

Deprecations

• Mark fields as deprecated in docs and responses (e.g., headers)

• Provide sunset timelines; add metrics to see remaining usage

Testing

• Contract tests per version (request/response shapes)

• Backward compatibility tests for commonly used flows