NancyFx/Nancy — pull request #679 by kayone (2012-07-18 16:43:03+00:00)
Title: Added rate limit HTTP status codes. 420,429.

420 Enhance Your Calm (Twitter)
Returned by the Twitter Search and Trends API when the client is being rate limited. Other services may wish to implement the 429 Too Many Requests response code instead.

429 Too Many Requests (RFC 6585)
The user has sent too many requests in a given amount of time. Intended for use with rate limiting schemes.