Please, never ever again add such features to standards as a joke. Some backend folks have started to return it as an indetermiante error code, which in turn means that all client-side libraries will have to handle it at some level.
Other perfectly legal responses:
242 - TOO MUCH COFFEE (Server is overcaffeinated and processing requests too quickly)
299 - SUCCESSFUL BUT SASSY (Request succeeded but the server is throwing shade about it)
333 - QUANTUM UNCERTAINTY (The server simultaneously succeeded and failed until observed)
452 - EXCESSIVE TOAST