You need select users (some without Google accounts) to upload images for 24 hours to test a Cloud ML Engine app. How should users upload images?

Signed URLs are ideal for granting temporary, time-limited access to specific Cloud Storage objects, even for users without Google accounts. You can generate a signed URL that allows uploads and set its expiration to 24 hours, perfectly matching the requirement. Using a password-protected bucket is not a standard Cloud Storage security mechanism and doesn't offer fine-grained, temporary access control. Creating an App Engine app for uploads introduces unnecessary complexity and operational overhead for a simple, temporary upload task. While Cloud Identity authentication would work for users with Google accounts, it doesn't address the requirement for users without Google accounts.