Restaurant Food Ordering System
What is the Restaurant Food Ordering System Problem?
Section titled “What is the Restaurant Food Ordering System Problem?”Design a restaurant food ordering system that allows customers to browse restaurants, place orders, track deliveries, and rate restaurants and delivery agents. The system should manage multiple restaurants with menus, handle order placement from multiple restaurants, assign delivery agents based on location, process payments through multiple methods, and send real-time notifications for order updates.
In this problem, you’ll design a system that coordinates between customers, restaurants, and delivery agents, handling complex workflows like order state transitions, payment processing, and real-time tracking.
Problem Overview
Section titled “Problem Overview”Design a scalable food ordering platform that connects customers with restaurants and delivery agents, managing the complete order lifecycle from placement to delivery.
Core Requirements
Section titled “Core Requirements”Functional Requirements:
- Restaurant Management: Manage multiple restaurants, each with unique menus, cuisines, locations, and ratings.
- Menu Management: Handle menu items organized by categories, set availability status, and update pricing.
- Order Placement: Allow customers to browse restaurants, view menus, and place orders with multiple items and quantities.
- Order Tracking: Track order status through lifecycle stages: Placed, Confirmed, Preparing, Out for Delivery, Delivered.
- Delivery Assignment: Assign delivery agents to orders based on location proximity and availability using configurable assignment strategies.
- Real-time Tracking: Provide real-time tracking of delivery agents and order status updates.
- Payment Processing: Support multiple payment methods (Credit/Debit Card, Digital Wallet, Cash on Delivery) with secure processing.
- Rating System: Allow customers to rate restaurants and delivery agents after order completion with optional text reviews.
- Promotions: Manage discounts, coupons, and promotional offers that can be applied to orders.
- Notifications: Send notifications to customers, restaurants, and delivery agents for order status updates and promotions.
- Concurrency: Handle concurrent order placements, delivery assignments, and status updates safely without data corruption.
Non-Functional Requirements:
- Object-Oriented Design: Clear separation of concerns with well-defined roles for each class.
- Extensibility: Easy to add new order states, payment methods, delivery assignment strategies, and notification channels without modifying existing code.
- Thread Safety: Order status transitions and delivery assignment algorithms should be safe from race conditions.
- State Management: Maintain a clear state flow with valid transitions and prevent invalid state changes.
- Real-time Updates: Support real-time updates with low latency for order tracking and notifications.
- Maintainability: Core logic should be testable, maintainable, and follow design patterns appropriately.
What’s Expected?
Section titled “What’s Expected?”1. System Architecture
Section titled “1. System Architecture”The system acts as a coordinator between customers, restaurants, and delivery agents.
2. Key Classes to Design
Section titled “2. Key Classes to Design”classDiagram
class Order {
-OrderState currentState
-List~OrderItem~ items
-DeliveryAgent deliveryAgent
-Payment payment
+confirm()
+startPreparing()
+outForDelivery()
+deliver()
+calculateTotal()
}
class OrderState {
<<interface>>
+confirm(order)
+startPreparing(order)
+outForDelivery(order)
+deliver(order)
}
class PaymentStrategy {
<<interface>>
+processPayment(amount, details)
}
class DeliveryAssignmentStrategy {
<<interface>>
+assignAgent(order, agents)
}
Order --> OrderState
Order --> PaymentStrategy
Order --> DeliveryAssignmentStrategy
Order "1" -- "many" OrderItem
System Flow
Section titled “System Flow”Order Lifecycle Flow (State Transitions)
Section titled “Order Lifecycle Flow (State Transitions)”
Key Design Challenges
Section titled “Key Design Challenges”1. Managing Order State Transitions
Section titled “1. Managing Order State Transitions”Orders must transition through states in a specific order: Placed → Confirmed → Preparing → Out for Delivery → Delivered. Invalid transitions should be prevented.
Solution: Use the State Pattern. Create state classes (PlacedState, ConfirmedState, etc.) that encapsulate state-specific behavior and enforce valid transitions. Each state knows which transitions are allowed.
2. Supporting Multiple Payment Methods
Section titled “2. Supporting Multiple Payment Methods”The system needs to support different payment methods (Card, Wallet, COD) with different processing logic.
Solution: Use the Strategy Pattern. Create PaymentStrategy interface with implementations (CardPaymentStrategy, WalletPaymentStrategy, CODPaymentStrategy). The Payment class uses the strategy to process payments, allowing new payment methods to be added without modifying existing code.
3. Assigning Delivery Agents Intelligently
Section titled “3. Assigning Delivery Agents Intelligently”Delivery agents should be assigned based on different criteria (nearest, least busy, etc.) that may change based on business requirements.
Solution: Use the Strategy Pattern for delivery assignment. Create DeliveryAssignmentStrategy interface with implementations (NearestAgentStrategy, LeastBusyStrategy). The OrderService can swap strategies at runtime.
4. Real-time Notifications
Section titled “4. Real-time Notifications”Multiple parties (customers, restaurants, delivery agents) need to be notified when order status changes.
Solution: Use the Observer Pattern. The Order class maintains a list of OrderObserver references. When order status changes, all observers are notified. NotificationService implements OrderObserver to send notifications.
5. Concurrent Order Processing
Section titled “5. Concurrent Order Processing”Multiple customers may place orders simultaneously, and multiple delivery agents may be assigned concurrently.
Solution: Use thread-safe data structures (ConcurrentHashMap, CopyOnWriteArrayList) and synchronized blocks for critical sections. Fine-grained locking (per-order) reduces contention compared to system-wide locking.
What You’ll Learn
Section titled “What You’ll Learn”By solving this problem, you’ll master:
- ✅ State Pattern - Managing complex, multi-step lifecycles with valid transitions.
- ✅ Strategy Pattern - Implementing swappable algorithms for payment processing and delivery assignment.
- ✅ Observer Pattern - Decoupling notification logic from order management.
- ✅ Concurrency Control - Using locking mechanisms and thread-safe collections to prevent data corruption.
- ✅ Real-world System Design - Coordinating multiple actors (customers, restaurants, delivery agents) in a high-stakes environment.
View Complete Solution & Practice
Section titled “View Complete Solution & Practice”Ready to see the full implementation? Open the interactive playground to access:
- 🎯 Step-by-step guidance through the 8-step LLD approach
- 📊 Interactive UML builder to visualize your design
- 💻 Complete Code Solutions in Python, Java, C++, TypeScript, JavaScript, C#
- 🤖 AI-powered review of your design and code
Related Problems
Section titled “Related Problems”After mastering the Restaurant Food Ordering System, try these similar problems:
- Restaurant Management System - Focuses on table management and reservations.
- Payment Processor - Focus on payment processing and third-party integration.
- Notification Service - Handling multiple notification channels and delivery.