1.1.1 REST APIs
REST over HTTP uses URLs for resources (/orders/42) and methods for actions (GET, POST, PUT, PATCH, DELETE). Status codes tell the client what happened.
Why it matters
Almost every backend talks HTTP. Consistent APIs are easier to cache, document, and evolve.
How it is used
Return JSON. Use 201 on create, 204 on empty success, 400 for bad input, 404 when missing, 409 on conflict. Version only when you must. Keep payloads boring and explicit.