HLD prep is optimised for larger screens
Open on a laptop or desktop (1024px+) for the diagram canvas and the section sidebar side-by-side.
Problem Understanding
Restate the problem in your own words.
Design Google Drive / Dropbox
Design Google Drive: cloud-stored files of any size, multi-device sync (desktop + mobile + web), shared folders with permissions, version history, and conflict resolution when two devices edit while disconnected. The hard parts are chunked + deduplicated storage at exabyte scale, the sync protocol that has to converge on every reconnect, and the permissions model that scales to billions of files. Reads dominate, but the consistency expectation around shared folders is high — a permission revoke must propagate fast.
- Google Drive~1B users, files from a few KB to multi-GB. Tightly coupled with Docs / Sheets / Slides for in-place editing.
- DropboxThe original cloud sync service. Famously efficient delta-sync (only changed blocks ride the wire).
- OneDriveMicrosoft’s sync — deep Windows Explorer integration; Office 365 documents are the canonical clients.
- iCloud DriveApple’s sync — device-coupled and end-to-end-encryptable for sensitive folders.
Your task: read the problem above, then write what the system is, who uses it, the rough scale, and the headline UX expectation — in your own words. Submit for AI review when you're ready.
Click any step in the sidebar to jump around — sections don't have to be done in order. Press ? any time to see all shortcuts.