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428 Precondition Required
The 428 status code indicates that the origin server requires the request to be conditional.
Its typical use is to avoid the "lost update" problem, where a client GETs a resource's state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict. By requiring requests to be conditional, the server can assure that clients are working with the correct copies.
Responses using this status code SHOULD explain how to resubmit the request successfully.
The 428 status code is optional; clients cannot rely upon its use to prevent "lost update" conflicts.
Wikipedia
The origin server requires the request to be conditional. Intended to prevent "the "lost update"
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