429 Too Many Requests response status code indicates the user has sent too many requests in a given amount of time ("rate limiting").
Retry-After header might be included to this response indicating how long to wait before making a new request.
429 Too Many Requests
HTTP/1.1 429 Too Many Requests Content-Type: text/html Retry-After: 3600
|RFC 6585, section 4: 429 Too Many Requests||Additional HTTP Status Codes|