NestJS File Uploads

安全的文件处理、数据校验与 S3 流式传输。

SKILL.md

--- frontmatter

name: NestJS File Uploads
description: Secure file handling, Validation, and S3 streaming.
metadata:
  labels: [nestjs, upload, multer, s3]
  triggers:
    files: ['**/*.controller.ts']
    keywords: [FileInterceptor, Multer, S3, UploadedFile]

File Upload Patterns

Priority: P0 (FOUNDATIONAL)

Secure file upload handling with validation and storage patterns.

•
Magic Bytes: NEVER trust content-type header or file extension.
- •Tool: Use file-type or mmmagic to verify the 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: This is the only way to scale file uploads infinitely.

Processing

•Async: Don't process images/videos in the HTTP Request.
•
Flow:
1. •Upload file.
2. •Push FileUploadedEvent to Queue (BullMQ).
3. •Worker downloads, resizes/converts, and re-uploads.