Implementing secure file uploads to Amazon S3 at the edge: Choosing the right pattern

This article explains how to implement secure file uploads to Amazon S3, comparing PUT and POST operations, and presenting a serverless architecture combining S3 Transfer Acceleration and CloudFront.

• S3 PUT operations: Direct, idempotent, ideal for programmatic uploads with known file characteristics
• S3 POST operations: Browser-based, non-idempotent, designed for HTML forms with automatic key generation
• PUT uses runtime HTTP header signing; POST uses pre-generated policy documents in form fields
• S3 Transfer Acceleration routes uploads through edge locations for optimized global performance
• CloudFront provides additional security: WAF integration, geographic restrictions, edge computing, custom domains
• Reference architecture combines CloudFront, API Gateway, Lambda, Cognito, and S3 Transfer Acceleration
• Multi-layer security: OAC for static content, presigned POST policies, KMS encryption, JWT authentication
• Upload validation occurs at client, presigning, and S3 policy enforcement stages

The article provides patterns for choosing between PUT/POST operations and demonstrates a complete serverless solution for secure, branded, globally-optimized file uploads.