409 Conflict response status code indicates a request conflict with current state of the target resource.
Conflicts are most likely to occur in response to a
PUT request. For example, you may get a 409 response when uploading a file which is older than the one already on the server resulting in a version control conflict.
|RFC 7231, section 6.5.8: 409 Conflict||Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content|