Code Execution Platform (LeetCode / Replit) — Simple

Problem statement (interviewer prompt)

Design a code execution platform (LeetCode / Replit / Judge0): users submit code in any of 30+ languages, you compile + run it in a sandbox against test cases, return the result in seconds, and prevent abuse (CPU/memory/network/file-system limits).

flowchart LR
  U([User])
  API[Submit API]
  Q[[Job Queue]]
  WORK([Sandbox Worker])
  RES[Result store]
  U --> API --> Q --> WORK --> RES --> U

    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 client;
    class API service;
    class RES datastore;
    class Q queue;
    class WORK compute;