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Quiz Platform — Detailed#

flowchart TB
  subgraph Host
    HUI[Host UI]
  end

  subgraph Players
    PUI[Player apps]
  end

  subgraph Edge
    GW
    WS[WS gateway]
  end

  subgraph Session[Per-room session]
    SVR[Session owner]
    Q[[Question queue]]
    TIMER[Per-question timer]
    INPUT[Answer collector]
    SCORE[Score calculator]
    LDB[(In-memory leaderboard)]
  end

  subgraph Content
    BANK[(Question bank)]
    MEDIA[Media + CDN]
  end

  subgraph Persist
    HIST[(Game history)]
    USER[(Users)]
    META[(Rooms / codes)]
  end

  subgraph Anti
    DUP[Dup answer dedup]
    BOT[Bot / cheat detection]
  end

  Host --> Edge --> Session
  Players --> Edge --> Session
  Session --> Content
  Session --> Persist
  Anti --- Session

    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 WS,MEDIA edge;
    class HUI,PUI,SVR,TIMER,INPUT,SCORE,DUP,BOT service;
    class BANK,HIST,USER,META datastore;
    class LDB cache;
    class Q queue;

Real-time fairness#

  • Server is authoritative on timing; client clocks not trusted.
  • Player answer counted only after server-side timer started.
  • Score combines correctness + speed bonus.

Scale#

  • Live rooms range from 5 to 100k participants (Kahoot+).
  • Per-room state in memory; periodic snapshot for crash recovery.

Glossary & fundamentals#

Concepts referenced in this design. Each row links to its canonical page; the tag column shows whether it is a high-level (HLD) or low-level (LLD) concept.

Tag Concept What it is Page
HLD CDN edge caching for static assets cdn