You need to securely share a single object from a private S3 bucket with several users who do not have AWS accounts. Which approach is the most operationally efficient?

Generating a presigned URL is the most operationally efficient method because it grants temporary, time-limited access to a specific S3 object without requiring AWS credentials or accounts for the users. You simply create the URL and share it. Applying an S3 bucket policy based on IP addresses is less flexible and efficient, as user IP addresses can change, and it doesn't scale well for multiple users. Creating an IAM role and asking users to assume it is not feasible for users without AWS accounts. Making IAM users and distributing credentials is a security risk and operationally burdensome, as it requires managing credentials for external users.