Design a Restaurant Management System

Design a Restaurant Management System that handles table reservations, order placement, billing, and menu management.

What is the Restaurant Management Problem?

Design a Restaurant Management System that handles table reservations, order placement, billing, and menu management. The system should manage table availability, detect reservation conflicts, track order status, and generate bills with tax and tip calculations. The system should support concurrent reservation requests while maintaining data consistency.

In this problem, you’ll design a system that manages the entire customer journey—from booking a table to paying the bill—while coordinating between the dining area, the kitchen, and the billing desk.

Problem Overview

Design a system to streamline restaurant operations, focusing on efficient table turnover, order accuracy, and transparent billing.

Core Requirements

Functional Requirements:

Table Management: Track states (Available, Reserved, Occupied, Cleaning) and capacities.
Reservations: Book by date, time, and party size; automatically assign smallest suitable table.
Conflict Prevention: Detect and prevent overlapping reservations for the same table.
Menu Management: Organize items by category with detailed pricing.
Order Flow: Place orders associated with tables; track status (Placed → Preparing → Served → Completed).
Billing: Generate bills including item prices, tax, and optional tip percentages.
Pricing Strategies: Support different models (Happy Hour, Seasonal) and discounts (Percentage, Fixed).
Order Types: Handle different fulfillment modes (Dine-in, Takeout) using Factory Pattern.
Concurrency: Manage simultaneous reservation requests safely to avoid double-booking.

Non-Functional Requirements:

Separation of Concerns: Clear OOD roles for Restaurant, Table, Reservation, Order, and Bill.
Extensibility: Easy to add new table states, order statuses, or payment methods.
Efficiency: Optimized algorithms for conflict detection and table assignment.
Thread Safety: Ensure data consistency during concurrent updates to reservations or orders.

What’s Expected?

1. System Architecture

The system coordinates between the ReservationService, OrderManager, and BillingService.

2. Key Classes to Design

classDiagram
    class Table {
        -int id
        -int capacity
        -TableState state
        +reserve()
        +occupy()
    }
    
    class Order {
        -String id
        -Table table
        -List~OrderItem~ items
        -OrderStatus status
        +addItem(item)
        +calculateSubtotal()
    }
    
    class MenuItem {
        -String name
        -double price
        -Category category
    }

    class Reservation {
        -Customer customer
        -Table table
        -DateTime startTime
        -int partySize
    }

    Table "1" -- "0..1" Reservation
    Table "1" -- "many" Order
    Order "1" *-- "many" OrderItem
    OrderItem --> MenuItem

System Flow

Order to Bill Flow

Key Design Challenges

1. Smart Table Assignment

If a party of 2 arrives, you shouldn’t put them at a table for 8 if a table for 2 is available.

Solution: Implement a Table Assignment Strategy. The system searches for the smallest available table that fits the party size (table.capacity >= partySize) and matches the requested time slot.

2. Reservation Conflicts

Checking if a table is free for a 2-hour window requires checking all other reservations for that specific table.

Solution: Use Interval Overlap Detection. A new reservation [startA, endA] conflicts with an existing one [startB, endB] if startA < endB AND startB < endA. This check must be performed within a database transaction or a synchronized block.

3. Dynamic Bill Modifiers

A bill might have a 10% Happy Hour discount, a 5% service charge, and a 8% tax.

Solution: Use the Decorator Pattern or Strategy Pattern. The BillCalculator can apply a chain of modifiers (Tax, Discount, ServiceCharge) to the subtotal. This makes it easy to add or remove specific charges without changing the core billing logic.

What You’ll Learn

By solving this problem, you’ll master:

✅ Resource Scheduling - Managing time-based allocation of physical assets.
✅ State Transitions - Coordinating complex lifecycles for tables and orders.
✅ Financial Logic - Building robust and extensible billing engines.
✅ Concurrency Control - Handling high-volume booking and updates safely.

View Complete Solution & Practice

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