Dropbox File Storage System Design

System design for a cloud file storage service like Dropbox. Covers presigned URL uploads to S3, CDN-backed downloads, metadata storage in DynamoDB, file sharing with normalized SharedFiles table, and cross-device sync via notification service.

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Dropbox File Storage System Design
Requirements

Functional

  • Upload a file from any device
  • Download a file from any device
  • Share files with other users
  • Automatically sync files across devices

Non-Functional

  • Highly available (availability over consistency)
  • Support files up to 50GB
  • Secure and reliable with file recovery
  • Low latency uploads, downloads, and sync
Published
February 16, 2026

Last updated February 16, 2026

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