Google Drive — Mock Interview

You're designing Google Drive for a live system-design interview: a file storage, sync, and sharing service. Users upload files from a laptop, phone, or the web, and every change must appear — up to date — on all their other devices and anyone they've shared with. The heart of the problem is doing this at massive scale without re-uploading gigabytes on every edit.

Scale assumptions:

• ~1B registered users; ~100M daily active; ~50 GB stored per user on average.
• Files stored as content-addressed 4 MB chunks, deduplicated globally.
• ~20 file changes/day per active user; changes must sync to other devices in a few seconds.
• Durability is paramount: an uploaded file must essentially never be lost.

We'll move through requirements, estimation and data model, the high-level architecture, a deep dive on chunking/dedup/sync (the crux), and tradeoffs at scale. Think out loud and state your assumptions.