F1: Real-Time Geospatial Driver-Rider Dispatch & Matching

1. Description & Telemetry Flow

Captains log into their portal (CaptainHome.jsx) and connect to the central WebSocket server (socket.js). As the captain drives, their browser emits update-location-captain events with longitude and latitude. When a rider requests a pickup, the server identifies all online captains within the geographic radius and emits a new-ride payload directly to their socket rooms.

2. Dispatch Sequence Diagram

sequenceDiagram
    participant Rider
    participant Server as Express & Socket.io (:4000)
    participant Maps as Google Maps Distance Matrix
    participant Captain as Nearby Captains

    Captain->>Server: socket.emit('join', { userType: 'captain', userId })
    Captain->>Server: socket.emit('update-location-captain', { location: { lat, lng } })
    Rider->>Server: POST /rides/create (pickup, destination, vehicleType)
    Server->>Maps: Compute pickup/destination distance & duration
    Maps-->>Server: Return distance in meters & travel time
    Server->>Server: Query available captains within radius
    Server-->>Captain: socket.emit('new-ride', rideDetails)
    Captain->>Server: POST /rides/confirm (rideId, captainId)
    Server-->>Rider: socket.emit('ride-confirmed', { captain, vehicle, otp })

3. Say It Out Loud

"I engineered the real-time driver dispatch engine using Socket.io on top of Express. When a captain goes active, their client establishes a persistent WebSocket connection and joins a designated socket room keyed by their user ID. As they navigate, their device emits location updates that keep their in-memory geospatial coordinates fresh. When a rider creates a ride, the backend calculates the pickup distance and broadcasts a new-ride event exclusively to active captains within the proximity radius. I chose WebSockets over HTTP polling because it reduces dispatch latency from seconds to under 50 milliseconds, which is critical for ride-hailing responsiveness."