AWS S3 Storage (Python)

Use pre-signed PUT URLs to enable direct browser uploads to S3. Your Python backend validates the MIME type against an allowlist, generates a pre-signed URL for the browser, and then confirms the upload via head_object before persisting the object key.

The best way to validate file types for pre-signed S3 URL uploads is applying a server-side MIME allowlist before signing the PUT object request. This prevents risky or inefficient file handling by ensuring only authorized types are uploaded.

Store references to uploaded S3 objects by persisting only the S3 object key in your database. Avoid storing full URLs; instead, generate pre-signed GET URLs on demand when access-controlled downloads are needed.

An upload confirmation step verifies integrity by requiring a follow-up API call where the server checks object existence using head_object. This confirms the file actually exists in S3 before saving the object key reference to your database.

Yes, you can use boto3 to generate access-controlled download URLs for files stored in S3. By creating pre-signed GET URLs on demand, clients can securely download files without streaming file bytes through your server.

No, you do not need to stream file bytes through your server for access-controlled S3 downloads. By generating pre-signed GET URLs via boto3, the browser downloads files directly from S3 while maintaining access restrictions.