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.
dropboxfile storagesystem designcloud storagecdn
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
Author
Published
February 16, 2026
Last updated February 16, 2026