Voting System — Simple

Problem statement (interviewer prompt)

Design an election-grade voting system: eligible voters authenticate once and cast a single secret ballot that is auditable + verifiable + tamper-evident. Cover voter identity, ballot anonymity, end-to-end verifiability, and resistance to common attacks (bots, ballot stuffing, replay).

flowchart LR
  V[Voter]
  AUTH[Identity / Eligibility]
  BOOTH[Vote Service]
  LED[(Append-only ledger)]
  AGG([Aggregator])
  AUD[Auditors]
  V --> AUTH --> BOOTH --> LED --> AGG
  AUD --- LED

    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 V,AUTH,BOOTH,AUD service;
    class LED datastore;
    class AGG compute;