easy Drill: 5-year storage for a photo service
Drill
Users upload 5M photos/day, ~2 MB each (original + thumbnail). Retain 5 years, replicate ×3. Estimate total storage.
✅ Worked solution & bounds check
Worked solution
- Per day = 5 × 10⁶ × 2 MB = 10 TB/day.
- 5 years = 10 TB × 365 × 5 ≈ ~18 PB.
- ×3 replication ≈ ~55 PB.
Bounds: ignoring thumbnails ≈ 36 PB; with metadata overhead ≈ 60 PB.
Gate: tens of PB of immutable blobs ⇒ object storage (S3) + CDN, never a relational DB.
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