The customer must be able to download the generated video for at least 3 hours, which requires durable storage that persists beyond the Lambda execution environment. The best fit is Amazon S3 with a presigned URL.

Lambda’s /tmp storage (Option A) is ephemeral and scoped to the execution environment. It is not intended for durable customer downloads and can be deleted when the execution environment is recycled. A Lambda function URL also does not solve durable file hosting and would require the function to serve the content itself.

Option C uses S3 to store the video object durably and then issues a presigned URL that grants time-limited access to that specific object. Presigned URLs are designed for exactly this scenario: allow unauthenticated users temporary access to a private S3 object without making the bucket public. The developer can set the URL expiration to 3 hours (or longer), meeting the access requirement cleanly.

Option B is incorrect because S3 presigned URLs are for S3 objects, not EFS files. EFS does not natively use S3-style presigned URLs for external downloads.

Option D is not the right model: CloudFront can distribute S3 content and supports signed URLs/cookies, but CloudFront is a distribution layer, not an origin storage solution by itself. You would still need to store the video in S3 (or another origin). For the stated requirement, S3 + presigned URL is simpler and has less overhead.

Therefore, store videos in Amazon S3 and provide presigned URLs with a 3-hour expiration.