Why versioning matters before your first external client
Internal consumers will bake assumptions into dashboards and scripts the moment endpoints go live. Treat every stable route as a contract.
URL path versioning
Prefixes like /v1/ are easy to route, cache, and document. They are verbose but explicit — ideal for partner-facing APIs.
Header-based negotiation
Headers reduce URL churn but complicate caching and debugging. If you choose headers, document them in OpenAPI and enforce them in integration tests.
Deprecation policy
Publish sunset dates, return warning headers, and log traffic to deprecated routes. Give integrators at least one release cycle of overlap when breaking fields change.
Documentation and examples
Machine-readable specs plus worked examples reduce support load. Regenerate docs in CI so examples never drift from reality.
Compatibility tests
Maintain contract tests or consumer-driven checks for top partners. They catch accidental breaking changes before deploy.