Requirements

Imagine you're building the backend for an airline seat reservation system. It's not just about marking seats as taken. We need a robust system that handles seat assignments based on passenger preferences (window, aisle), manages different fare classes (First, Business, Economy), deals with flight changes, and ensures that the seat map remains consistent even under heavy load. The system should also be easily extensible to accommodate new types of aircraft and seating configurations without requiring major code rewrites. This problem focuses on the core seat reservation logic and doesn't include external services like payment processing or flight scheduling. # Requirements ## Functional Requirements 1. **Aircraft Configuration:** The system must support different aircraft types, each with a unique seating configuration (number of rows, seats per row, and seat types – window, aisle, middle). 2. **Seat Availability:** The system needs to track the availability of each seat on a flight. 3. **Seat Reservation:** Passengers should be able to reserve specific seats based on their preferences (window, aisle, or no preference). 4. **Fare Class Assignment:** Seats should be assignable to different fare classes (First, Business, Economy). The number of seats allocated to each fare class can vary per flight. 5. **Seat Assignment Rules:** Implement rules for seat assignment. For example, priority should be given to passengers with specific fare classes (First Class gets preferred seats). Consider families traveling together, offering seats in the same row if possible. 6. **Seat Unreservation/Cancellation:** Passengers should be able to cancel their reservations, freeing up the seat. 7. **Flight Changes:** The system must handle scenarios where flights are changed or canceled. Passengers with reservations on the original flight should be automatically re-accommodated on the new flight, prioritizing their original seat preferences if possible. If their original seat type is unavailable, the system should find a suitable alternative. 8. **Passenger Manifest:** The system must be able to generate a passenger manifest for a given flight, listing all passengers and their assigned seats. 9. **Seat Upgrade/Downgrade:** Passengers should be able to request upgrades or downgrades, subject to availability. 10. **Seat Map Display:** Allow displaying a seat map indicating occupied and available seats. ## Non-Functional Requirements 1. **Thread Safety:** The system must be thread-safe to handle concurrent reservation requests from multiple users without data corruption or race conditions. 2. **Extensibility:** The system should be designed to easily accommodate new aircraft types, seating configurations, fare classes, and seat assignment rules with minimal code changes. 3. **Modularity:** The system should be composed of loosely coupled modules to promote maintainability and reusability. 4. **Testability:** The system should be designed to facilitate unit testing of individual components and integration testing of the overall system. Consider dependency injection to aid in testing. 5. **Performance:** The system should be able to handle a large number of concurrent reservation requests with acceptable response times. While specific latency numbers are not crucial here, the underlying algorithms and data structures must be efficient (e.g., avoid brute-force searches). 6. **Scalability:** Although this is an in-memory exercise, the design should consider potential scalability challenges. For instance, think about how the data structures might need to be adapted for distributed storage in the future (e.g., using interfaces to abstract data access). ## Core Entities 1. **Aircraft:** Represents an aircraft type with its seating configuration (number of rows, seats per row, seat types). 2. **Seat:** Represents a specific seat on an aircraft, including its row number, seat letter, and type (window, aisle, middle). It also needs to track its current reservation status and associated fare class. 3. **Flight:** Represents a specific flight instance, including the aircraft being used, departure/arrival airports, and times. 4. **Passenger:** Represents a passenger with a unique identifier. 5. **Reservation:** Represents a passenger's reservation for a specific seat on a flight. 6. **SeatMap:** A representation of the available seats on a particular aircraft for a given flight. Should handle seat allocation and deallocation. 7. **FareClass:** Represents a fare class (e.g., First, Business, Economy) and associated properties (e.g., priority for seat assignment). 8. **SeatAssignmentStrategy:** An interface to define different seat assignment algorithms. 9. **NotificationService:** An interface/class to handle notifications when seats are assigned, unassigned, or when other events occur.

Airline Seat Reservation System

Requirements

Interview Simulation

Functional Requirements

💡 Interview Tip

Non-Functional Requirements

Core Entity Identification

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