Gateway Gus saysYou’ve covered APIs end to end — now design and document one real, consistent API.
APIs click when you design one. The capstone: model a small domain as REST resources, write an OpenAPI spec, choose an auth scheme (bearer tokens), add pagination/filtering, define a consistent error shape, and pick caching + rate-limit rules. That proves you can ship an API others can build on. References: the HTTP RFCs, the OAuth 2.0 RFCs, the OpenAPI spec, and MDN's HTTP docs.
Power-ups you unlock
Build to retain — design + document one API
Resources + OpenAPI + auth + pagination + errors
Consistency is the deliverable
Refs: HTTP RFCs, OAuth RFCs, OpenAPI, MDN
Timeout Titan attacks — common mistakes
Designing endpoints with no written spec
Skipping auth/rate-limit/error decisions
Inconsistency that makes the API hard to learn
Boss battleDesign a "bookmarks" API: resources, auth, pagination, and one error shape.