Design a Cloud File Storage & Synchronization Service (Google Drive / Dropbox).

In Simple Words: Allow users to upload, download, and synchronize files of arbitrary size across desktop and mobile devices with automatic delta sync and data deduplication.

Core Innovations:

• Chunking (Delta Sync): Files are divided into 4MB chunks. When a user edits a 500MB document, only the modified 4MB chunks are re-uploaded, saving 99% bandwidth!
• Content-Addressable Storage: Each chunk is named after its SHA-256 hash. If multiple users upload the identical file, only one physical copy is stored in object storage (Global Deduplication).

flowchart TD
    Client["Client App"] --> ChunkEngine["Chunking Engine (4MB Chunks)"]
    ChunkEngine --> Hasher["SHA-256 Hash Generator"]
    Hasher --> MetaSvc["Metadata Service (PostgreSQL)"]
    MetaSvc -->|"Check if Chunk Exists"| S3["AWS S3 / GCS Object Storage"]
    Hasher --> S3