Round 1: DS/PS

• Gas Station
• Singleton class and implementation.
• final, static, transient, synchronized and volatile keywords and their usage.
• Immutable class in Java and implementation.

Round 2: System Design

• Design a Dropbox like system (HLD)
• Requirements
  • Users can log in and log out.
  • Users can upload/download multiple files (file size limited to 1GB).
  • Daily Active Users - 1M
  • User uploads 1 file daily.
• Discussions
  • APIs: Login, logout, upload, and download.
  • File storage: Using cloud storage (e.g., AWS S3) and handling large files with chunk uploads.
  • Security: Adding user authentication (JWT) and encrypting files during upload/download.
• Follow-up:
  • How to allow users to share files to other users?

Final Verdict
Rejected after the second round.