File Upload Patterns

Priority: P0 (FOUNDATIONAL)

• Magic Bytes: NEVER trust content-type header or file extension.
• Tool: Use file-type or mmmagic to verify actual buffer signature.
• Limits: Set strict limits: { fileSize: 5000000 } (5MB) in Multer config to prevent DoS.

Streaming (Scalability)

• Memory Warning: Default Multer MemoryStorage crashes servers with large files.
• Pattern: Use Streaming for any file > 10MB.
• Library: multer-s3 (direct upload to bucket) or busboy (raw stream processing).
• Architecture:

1. Client requests Signed URL from API.
2. Client uploads directly to S3/GCS (Bypassing API server completely).
3. Pro Tip: Only approach to scale file uploads infinitely.

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