I've seen 412 "precondition failed" returned when there is that sort of conflict. For example, Google Cloud Storage returns 412 if you try to replace exactly on

I've seen 412 "precondition failed" returned when there is that sort of conflict. For example, Google Cloud Storage returns 412 if you try to replace exactly one resource (defined as data + generation or etag) with new data: https://cloud.google.com/storage/docs/request-preconditions https://cloud.google.com/storage/docs/request-preconditions