Stock Exchange / Matching Engine — Simple

Problem statement (interviewer prompt)

Design the matching engine of a stock exchange (NYSE / Nasdaq-style). It must accept orders via FIX, run price-time priority matching for hundreds of symbols at microsecond latency, broadcast market data, replicate state to hot standbys, and feed clearing/settlement.

flowchart LR
  TR[Trader]
  GW[Order Gateway]
  RISK[Risk / PreTrade]
  ME[Matching Engine<br/>order book]
  FEED[Market Data Feed]
  CLR[Clearing & Settlement]
  TR --> GW --> RISK --> ME --> FEED
  ME --> CLR

    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 GW edge;
    class TR,RISK,ME,FEED,CLR service;