Pastebin — Simple

Problem statement (interviewer prompt)

Design a Pastebin: anyone can paste text, get a short URL, and others can read it. Support expiry, password-protect, syntax highlighting, edit/delete by owner, and view counters. Optimise for read-heavy (10:1) and 1M new pastes/day.

flowchart LR
  U([User])
  W([Web / API])
  ID([ID Generator])
  OBJ[(Object Storage<br/>paste body)]
  META[(Metadata DB<br/>id, owner, expiry)]
  CDN[CDN]
  U -->|POST /paste| W
  W --> ID
  W --> OBJ
  W --> META
  U -->|GET /:id| CDN --> W
  W --> META
  W --> OBJ

    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 U,W client;
    class CDN edge;
    class META datastore;
    class ID compute;
    class OBJ storage;