Regarding the author's recommendation against using 404: The author says it's ambiguous, because it could mean the route is not found, or it could mean the requested item is not found. Some people use 204 to indicate the latter: https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/204 It basically means, "We received and understood your request, but you're not getting a response." And you can infer that it's beca…
I like very much something I saw in the Dropbox API:
All application errors are returned with a 409 code, and then you are sure to have a properly json formatted error in the body that can will have an error code more relevant for your case.
So that could be NOT_FOUND in such a case.