HLD-235·Storage & Media
Medium · 1,000 ptsCloud Photo Backup, Dedup & Timeline Album Service
Design Google Photos / iCloud Photos metadata timeline, SHA-256 content deduplication, and shared event album delivery across mobile devices.
Max p99
≤ 55 ms
Availability
≥ 99.5%
Budget
≤ $5,650
Functional Requirements
- FR-1POST /photos/{user_id}/commit — Deduplicates blob hash, stores EXIF metadata, and appends timeline.
- FR-2GET /photos/{user_id}/timeline — Serves chronological photo grid and shared album thumbnails.
- FR-3PATCH & DELETE /photos/{user_id}/commit — Updates, cancels, or deletes user_id records and immediately invalidates or updates cached state (read-after-write).
- FR-4Uploader must immediately see newly backed-up photos (read-after-write) and survive 6x storage brownouts.
Workload Profile
Steady Camera Sync32,000 Timeline Read RPS / 4,500 Backup Write RPS
Holiday Event Shared Albums94,000 Read RPS / 12,000 Write RPS
Active Working Set28 GB hot timeline indexes & thumbnail URLs
Traffic DistributionBurst reads on viral shared wedding/holiday album_id & user_id
Consistency Model
Read-after-write timeline metadata visibility; raw media blobs content-addressed and immutable.
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