Design a Hotel Management System

Design a hotel management system that allows guests to search for available rooms, make reservations, check in, and check out.

What is the Hotel Management System Problem?

Design a hotel management system that allows guests to search for available rooms, make reservations, check in, and check out. The system should handle room management with different room types and amenities, check room availability for date ranges, manage reservations with proper state transitions, and apply pricing strategies based on room type and season.

In this problem, you’ll design a system that handles the entire guest lifecycle—from searching for a room to final check-out.

Problem Overview

Design a system to manage a single hotel’s operations, focusing on room inventory, reservation processing, and guest check-in/out flows.

Core Requirements

Functional Requirements:

Room Search: Search for available rooms for a specific date range.
Conflict Detection: Implement date range overlap detection to prevent double-bookings.
Booking Management: Allow creating and cancelling reservations (releases rooms back to Available).
Lifecycle Flow: Support check-in (Reserved → Occupied) and check-out (Occupied → Available) processes.
Room Hierarchy: Manage different room types (Single, Double, Suite) with varying base prices and amenities.
Dynamic Pricing: Apply rates based on room type and season (Peak vs. Off-season) using Strategy Pattern.
State Tracking: Monitor room statuses (Available, Reserved, Occupied, Maintenance) using State Pattern.
Guest History: Maintain guest information and their reservation history.

Non-Functional Requirements:

Consistency: Reservation operations must be thread-safe to handle concurrent booking attempts.
Modular Design: Separate room logic, reservation logic, and pricing strategies for high extensibility.
Testability: Core logic should be easy to validate through unit tests.
Extensibility: Easily add new amenities, membership tiers, or room types in the future.

What’s Expected?

1. System Architecture

The system revolves around the Hotel which acts as a container for rooms and a service for reservations.

2. Key Classes to Design

classDiagram
    class Hotel {
        -List~Room~ rooms
        +searchRooms(criteria)
        +bookRoom(guest, room, dates)
    }
    
    class Room {
        -int roomNumber
        -RoomType type
        -RoomState state
        +updateStatus()
    }
    
    class Reservation {
        -String id
        -Guest guest
        -Room room
        -DateRange dates
        -ReservationStatus status
        +cancel()
    }

    class PricingStrategy {
        <<interface>>
        +calculatePrice(room, dates)
    }

    Hotel --> Room
    Hotel --> Reservation
    Room --> RoomState
    Reservation --> PricingStrategy

System Flow

Reservation & Check-In Flow

Key Design Challenges

1. Preventing Double Bookings

Checking availability and creating a reservation must be an atomic operation. If two threads check at the same time, they might both see the room as available.

Solution: Use Synchronization or Locks. Wrap the booking logic in a synchronized block or use a ReentrantLock for the specific room to ensure only one reservation can be finalized at a time.

2. Complex Room States

A room isn’t just “Available” or “Full.” It might be “Reserved” (booked but not checked in), “Occupied,” “Being Cleaned,” or “Under Maintenance.”

Solution: Use the State Pattern. Encapsulate state-specific behavior (e.g., you can’t check in to a room that is “Being Cleaned”) in separate state classes, making the transitions clean and bug-free.

3. Dynamic Pricing

Prices change based on weekends, holidays, or room upgrades.

Solution: Use the Strategy Pattern. Create a PricingStrategy interface and implement various concrete strategies like SeasonalPricing, WeekendPricing, and BasePricing. The Reservation can apply these strategies based on the current context.

What You’ll Learn

By solving this problem, you’ll master:

✅ State Management - Handling complex object lifecycles.
✅ Availability Logic - Implementing date-range overlap detection.
✅ Concurrency Control - Building thread-safe booking systems.
✅ Design Patterns - Applying State, Strategy, and Factory in a real-world scenario.

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