flowchart LR
    C["fix-client-simulator<br/>Console + FIX initiator"]
    subgraph G["fix-gateway — Spring Boot"]
        F["FIX acceptor + mapper"]
        W["Bounded queue + workers<br/>Protobuf mapper + gRPC client"]
        E["ExecutionReport factory + delivery"]
        F --> W
        W -->|Definitive decision| E
    end
    O["order-management-service<br/>Validate + decide<br/>In-memory repository"]
    P["proto-contracts<br/>order.proto + generated Java"]
    C -->|"FIX NewOrderSingle — 9876"| F
    W -->|"gRPC SubmitOrder — 9090"| O
    O -->|"Response / status"| W
    E -->|"FIX ExecutionReport: original session"| C
    P -.-> W
    P -.-> O