HTTP 421 Mock Endpoint

HTTP 421 Misdirected Request indicates the request was directed at a server that cannot or will not produce a response. This is primarily an HTTP/2 concern — when connection coalescing routes a request over a shared connection to a server that isn't authoritative for the requested host. The client should retry the request over a different connection. CDNs and load balancers with multiple virtual hosts are the most common source of 421 errors.