To make sure that API clients do not overwrite each other's data, this API supports optimistic concurrency control for PUT operations by including an Etag
header. When the client updates a resource, it can include an optional If-Match
header with the ETag
header value it received from the GET. When the client provides an If-Match
header, the request succeeds if the state matches what the client is updating as indicated by the ETag
. Otherwise, it issues a 412 error.