問題文
A retailer's checkout service is being given an automatic retry so that transient failures of the downstream APIs stop reaching customers. The service calls four operations: a stock read, a stock reservation created with POST, a mandate replacement done with PUT, and a basket item removal done with DELETE. Where can the retry be applied safely?
選択肢
- To the three write operations, because a read can always be repeated by the caller later and the value of a retry lies in protecting the writes that would otherwise be lost
- To the stock read alone, because only an operation that changes nothing at all can be repeated, and any operation that writes has to be left to the customer to attempt again by hand
- To the stock read, the mandate replacement and the basket item removal, because repeating any of those leaves the same end state, while the reservation created with POST would produce a second reservation each time it is repeated
- To all four operations, because the downstream APIs are behind a gateway that recognizes a repeated request from the same caller and returns the response it gave the first time round without acting again