[Joker_vD]

> 200 is less than the 400 requested,

That's irrelevant. Otherwise, requests for 400 bytes against a resource that is actually only 200 bytes long would never be considered complete and would be disallowed to be cached.

[pornel]

TIL, the HTTP RFC explicitly allows range end to exceed the length of the content:

https://www.rfc-editor.org/rfc/rfc9110#name-byte-ranges