Design a File Storage Service like Dropbox or Google Drive

Functional Requirements:

• Users can upload files to their personal storage.
• Users can download their files at any time.
• Users can organize files into folders/directories.
• Users can share files or folders with other users (read-only or read-write permissions).
• Users can update or overwrite existing files.
• Users can delete files or folders.
• Users can view a list of their files and folders (home directory view).

Non-Functional Requirements:

• High durability: Files should not be lost once uploaded.
• High availability: Users should be able to access their files reliably.
• Scalability: The system should support millions of users and petabytes of data.
• Strong consistency: File operations (upload, update, delete) should be reflected immediately across all clients.
• Security: Only authorized users should be able to access files; sharing should be controlled by permissions.
• Reasonable response time: Directory listings should be fast (sub-second), uploads/downloads should be acceptable for large files (seconds).