Presigned URL
Also called: Signed URL
A temporary URL, signed by your server, that lets a client perform one specific action on object storage without credentials.
Definition
The server signs the bucket, key, HTTP method, expiry and optionally content type, size and checksum. The client uploads or downloads directly with the URL, so file bytes never pass through the API servers. Grants should be narrow: a server-chosen key, a short expiry, and limits on type and size. What arrives must still be verified before it is used.
In practice
The API returns a 15-minute PUT URL for uploads/u42/7f3a; the app sends the photo straight to S3.