How would you design a system like Uber

package com.bank.ridehailing.model;

import java.math.BigDecimal;

public class TripRequest {
    private String riderId;
    private double pickupLat;
    private double pickupLng;
    private double dropLat;
    private double dropLng;
    private BigDecimal estimatedFare;

    public TripRequest(String riderId, double pickupLat, double pickupLng,
                       double dropLat, double dropLng) {
        this.riderId = riderId;
        this.pickupLat = pickupLat;
        this.pickupLng = pickupLng;
        this.dropLat = dropLat;
        this.dropLng = dropLng;
    }

    // Getters omitted for brevity
    public String getRiderId() { return riderId; }
    public double getPickupLat() { return pickupLat; }
    public double getPickupLng() { return pickupLng; }
}

package com.bank.ridehailing.service;

import java.math.BigDecimal;

public class PaymentService {

    public PaymentResult chargeRider(String riderId, String tripId,
                                      BigDecimal fare, String idempotencyKey) {
        // Idempotency: if this key was already processed, return stored result
        // Outbox pattern: write payment + event in one transaction
        return new PaymentResult(tripId, "SUCCESS", idempotencyKey);
    }
}

package com.bank.ridehailing.location;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.GeoCoordinate;

public class DriverLocationStore {

    private final Jedis jedis;
    private static final String GEO_KEY = "drivers:active";

    public DriverLocationStore(Jedis jedis) {
        this.jedis = jedis;
    }

    public void updateLocation(String driverId, double lat, double lng) {
        jedis.geoadd(GEO_KEY, lng, lat, driverId);
    }

    public java.util.List<String> findNearby(double lat, double lng,
                                              double radiusKm) {
        return jedis.georadiusByMember(GEO_KEY, "pickup-point", radiusKm,
            redis.clients.jedis.params.geo.GeoRadiusParam.geoRadiusParam()
                .sortAscending().count(10))
            .stream()
            .map(r -> r.getMemberByString())
            .collect(java.util.stream.Collectors.toList());
    }
}

# Driver D101 at 28.6139, 77.2090 (New Delhi)
# Driver D102 at 28.6150, 77.2100
# findNearby(28.6145, 77.2095, 2.0) returns [D102, D101]

package com.bank.ridehailing.matching;

import java.util.List;
import java.util.Optional;

public class MatchingEngine {

    private final DriverLocationStore locationStore;
    private final DriverAvailabilityStore availabilityStore;

    public MatchingEngine(DriverLocationStore locationStore,
                          DriverAvailabilityStore availabilityStore) {
        this.locationStore = locationStore;
        this.availabilityStore = availabilityStore;
    }

    public Optional<String> findAndClaimDriver(double pickupLat, double pickupLng) {
        List<String> candidates = locationStore.findNearby(pickupLat, pickupLng, 5.0);
        for (String driverId : candidates) {
            // Atomic claim: compare-and-set from AVAILABLE to ASSIGNED
            boolean claimed = availabilityStore.tryClaimDriver(driverId);
            if (claimed) {
                return Optional.of(driverId);
            }
        }
        return Optional.empty();
    }
}

package com.bank.ridehailing.model;

import java.math.BigDecimal;
import java.time.Instant;

public class Trip {
    private String tripId;
    private String riderId;
    private String driverId;
    private String status; // REQUESTED, MATCHED, IN_PROGRESS, COMPLETED, CANCELLED
    private double pickupLat;
    private double pickupLng;
    private double dropLat;
    private double dropLng;
    private BigDecimal fare;
    private Instant createdAt;
    private Instant completedAt;

    // Constructor and getters omitted for brevity
}

package com.bank.ridehailing.event;

public class TripStateChangedEvent {
    private String tripId;
    private String previousStatus;
    private String newStatus;
    private long timestamp;

    public TripStateChangedEvent(String tripId, String previousStatus,
                                  String newStatus) {
        this.tripId = tripId;
        this.previousStatus = previousStatus;
        this.newStatus = newStatus;
        this.timestamp = System.currentTimeMillis();
    }

    // Published to Kafka topic "trip-events"
    // Consumed by: notification-service, analytics-service, billing-service
}

package com.bank.ridehailing.security;

public class ApiGatewayFilter {

    public boolean authenticate(String token) {
        // Validate JWT, check expiry, extract rider/driver role
        return true; // simplified
    }

    public boolean authorize(String role, String resource) {
        // Rider can only access own trips
        // Driver can only access own offers
        return true; // simplified
    }
}

# Geographic partitioning example:
# Region: Delhi  -> partition-0 -> Redis Geo shard-0
# Region: Mumbai -> partition-1 -> Redis Geo shard-1
# Region: Bangalore -> partition-2 -> Redis Geo shard-2
# A busy city's load stays within its own shard