421 Misdirected Request
Meaning
The request was directed to a server that is not able to produce a response (for example, the request was sent to the wrong server due to reuse of a connection).
When to Use
When the server host name in the request (URL) doesn’t match the server that received the request, often due to a connection reuse or misconfiguration in HTTP/2. The server signals that it cannot respond because it wasn’t meant to receive that request.
Example
In an HTTP/2 connection, if a client erroneously reuses a connection for the wrong host, that server may respond with 421 Misdirected Request, telling the client to retry on a correct connection.
When Not to Use
Do not use for general routing failures. This is specific to scenarios like virtual host misrouting. If the request is correctly routed but fails for other reasons, use a different status code.
Source
RFC 9110