API contracts outlive a single deployment. This track follows a permit case service through response changes, incompatible units, a planned old-route retirement, and a release matrix with region lag and offline browser clients. Each lesson names the evidence needed before a server can stop honoring an earlier representation.
Topics in this track
- Response Shape Evolution and Unknown Values — Change response fields and enums while old clients, cached bundles, and offline requests still exist.
- API Version Selection and Representation Scope — Version incompatible representations explicitly and keep selection consistent across caches and links.
- Deprecation, Sunset, and Consumer Evidence — Retire an API only after identifying consumers, communicating dates, and testing a safe shutdown.
- Consumer Contract Matrix and Expand-Contract Release — Run old and new clients against intermediate server states before deleting old fields or routes.
Prerequisite paths
API Evolution and Compatibility Windows; Tests across boundaries: assert behavior, not implementation text; Deployment and Scale.
Practice and check
Build Project: permit API client migration and review Web Development: API contract migration quiz.