Advantage of authorizing direct call vs pre-signed URL for upload

Both pre-signed URLs and direct authorization for uploading to S3 have their own advantages, but they primarily differ in terms of security, flexibility, and complexity.

Pre-signed URLs are simple and secure for limited operations like uploading to S3. They are temporary, provide a secure, time-bound way for your IoT devices to upload directly without exposing broader permissions, and require minimal IAM configuration. However, they require a Lambda function to generate the URL and some additional client-side logic to handle the upload. Pre-signed URLs are a great choice when you want to limit what your IoT devices can do to very specific, controlled actions without broader access to AWS services.

Direct authorization, on the other hand, provides more flexibility, allowing the IoT devices to interact directly with multiple AWS services (like S3, DynamoDB, etc.) via appropriate IAM roles. While this can simplify authorization across services, it introduces greater complexity in terms of managing fine-grained IAM permissions and ensuring secure access. Direct authorization is useful when you need your devices to perform a variety of tasks beyond just uploading to S3, but it can increase the risk of misconfigurations or overly broad permissions.

The choice between pre-signed URLs and direct authorization depends on the scope of tasks your IoT devices need to perform. For simple, controlled uploads, pre-signed URLs are easier to manage and secure. If broader service interaction is needed, direct authorization may offer more flexibility but comes with added complexity and security considerations.