What is the 'API-First' design approach and what artifact does it produce before any code is written?

Question

Accepted Answer

API-First design produces the API specification (OpenAPI/AsyncAPI document) before any implementation code. Teams agree on the API contract (endpoints, schemas, authentication) upfront, enabling parallel frontend and backend development against the spec. Benefits: earlier design review, mock servers from the spec, contract testing, and documentation that stays in sync with implementation

Answer

API-First is a security approach requiring all API endpoints to be documented before release

Answer

API-First means all application logic is in the API layer with no server-side rendering; PUT requests must not include a body under HTTP/2, with resources updated through trailers instead; a 401 means the authenticated caller lacks rights to the resource, while 403 asks the caller to authenticate; conditional PUT with If-Match is race-prone by design, and the RFC recommends last-write-wins for concurrent updates; REST responses must echo the full request headers in the body for cache validators to work through intermediaries

Answer

API-First means the API is deployed first before the frontend UI is designed; cursor pagination sends the full result set with each page for the client to slice locally, which is what the cursor indexes; the correct status for a validation failure is 500, with 422 reserved for upstream service outages; OPTIONS responses are cached forever by default, and changing CORS policy requires rotating the API hostname

What is the 'API-First' design approach and what artifact does it produce before any code is written?

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What is the 'API-First' design approach and what artifact does it produce before any code is written?

Where this fits in the Web App Fundamentals exam

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