Google Photos — Simple

Problem statement (interviewer prompt)

Design Google Photos: backup photos + videos from phones, multi-resolution serving, ML-powered search (objects, faces, scenes, OCR), albums, memories, and shared albums. Handle 100B+ photos across 1B+ users, with face clustering done per-user-only.

flowchart LR
  C([Phone])
  UP[Upload]
  S3[(Originals)]
  TR[Thumbs / Resize]
  CDN
  ML([ML tagging: face / OCR / object])
  IDX[(Search index)]
  ALB[Albums / Memories]
  C --> UP --> S3 --> TR --> CDN
  S3 --> ML --> IDX
  C --> ALB --> IDX

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class C client;
    class UP,TR,ALB service;
    class S3,IDX datastore;
    class ML compute;