An ordinary signed delivery URL is not an expiry policy

A fictional application must provide a sensitive media file only during an authorized limited access window. A developer presents an ordinary signed delivery URL and says it must expire because a separate upload-authentication signature uses a timestamp. The supplied design has not selected a supported temporary download, token or equivalent lifetime mechanism, and the private/derived-asset behavior has not been reviewed. This case performs no upload or media request. It asks the learner to distinguish operation-specific signing from an actual supported viewing lifetime and to identify the access and cache conditions that must be verified before the application promises that every previously issued URL becomes unusable at a particular time.