✈️ Flight Booking Management System (FBMS)

The Flight Booking Management System (FBMS) is a distributed, microservices and event-driven-based airline reservation platform designed to replicate real-world flight booking workflows with a strong focus on scalability, consistency, and fault tolerance.

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The system enables passengers to seamlessly:

• 🔍 Search flights based on source, destination, and travel date
• 🎟️ Select seats using a real-time seat map
• 📖 Create and manage bookings
• 💳 Complete secure payment transactions
• 📩 Receive instant booking confirmations and notifications

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🧩 Problem it Solves

In real-world booking systems, challenges such as concurrent seat selection, payment failures, and system scalability can lead to inconsistent data (e.g., double booking).

FBMS addresses these challenges by implementing:

• 🔒 Seat Locking Mechanism to prevent double booking
• 🔄 Booking Lifecycle Management for controlled state transitions
• ⚡ Event-Driven Communication (Kafka) for asynchronous processing
• 🔐 JWT Authentication for secure and stateless interactions

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🏗️ How the System Works (High-Level Flow)

The system supports both Passenger Operations and Admin Operations, ensuring complete control over flight inventory and booking workflows.

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👨‍✈️ Admin Flow (System Management)

1. Admin logs in with privileged access
2. Admin can:
   • ✈️ Add new aircrafts (seat configuration, capacity)
   • 🛫 Create flights and schedules
   • 🛠️ Update or delete flights (CRUD operations)
3. When a flight is created:
   • Aircraft is mapped to the flight
   • Seat map is generated dynamically
4. These flights become immediately available in the system
5. Users can search and view these flights in real-time

💡 Admin acts as the source of flight inventory data

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👤 Passenger Flow (Booking Journey)

1. User registers / logs in
2. Searches for available flights
3. System fetches data from Flight Inventory Service
4. User selects a flight and views seat map
5. User selects seat → initiates booking

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🔄 Booking & Payment Flow

6. Booking Service creates booking (REQUESTED)

7. Booking Service calls Flight Inventory → reserve seat

8. Flight Inventory:

   • If AVAILABLE → mark RESERVED
   • Else → reject request

9. Payment Service processes transaction

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✅ Success Scenario

10. Payment successful →

• Booking → CONFIRMED
• Seat → OCCUPIED
• Event published (BookingConfirmedEvent)

11. Notification Service:

• Sends Email/SMS confirmation

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❌ Failure Scenario

• Payment fails →
  • Booking → CANCELLED
  • Seat → RELEASED

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🔁 Continuous System Behavior

• Admin can continuously:
  • Add/update flights
  • Manage aircrafts
• Users always see latest available flights and seats
• Kafka ensures background processes (notifications) do not block user flow

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🎯 Key Takeaway

The system ensures:

• 🔒 Consistent seat handling
• 🔄 Controlled booking lifecycle
• ⚡ Real-time flight availability
• 🧩 Clear separation between Admin and User responsibilities

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🧠 Architectural Approach

The system is built using:

• Microservices Architecture (MSA)
  Each domain (User, Flight, Booking, Payment, Notification) is implemented as an independent service.

• Domain-Driven Design (DDD)
  Business logic is divided into bounded contexts ensuring clear separation of concerns.

• Event-Driven Architecture (EDA)
  Kafka is used for asynchronous communication, enabling loose coupling and high scalability.

• API Gateway Pattern
  A centralized gateway handles routing, authentication, and request filtering.

• Service Discovery (Eureka)
  Enables dynamic service registration and load balancing.

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🏗️ System Architecture

graph TD
    Client --> Gateway(API Gateway)

    Gateway --> UserService
    Gateway --> FlightInventoryService
    Gateway --> BookingService
    Gateway --> PaymentService
    Gateway --> NotificationService

    subgraph Infrastructure
        Eureka
        Kafka
        PostgreSQL
    end

    BookingService --> FlightInventoryService
    BookingService --> PaymentService
    BookingService --> Kafka
    Kafka --> NotificationService

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🐳 Dockerized Setup & Running

This project is fully containerized using Docker and Docker Compose, enabling all microservices and infrastructure components to run together seamlessly.

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📋 Prerequisites

Make sure the following are installed on your system:

• Docker
• Docker Compose

Verify installation:

docker --version
docker compose version

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🚀 Build and Start the System

From the project root directory, run:

docker compose up -d --build

This command will:

• Build all microservices
• Start containers in detached mode
• Create required Docker networks
• Launch infrastructure services automatically

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🌐 Access Services

Service	URL
Eureka Dashboard	http://localhost:8761
Kafka UI	http://localhost:9090
Frontend Application	http://localhost:3000
PostgreSQL	localhost:5432

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🛑 Stop the System

To stop all running containers:

docker compose down

To remove volumes as well:

docker compose down -v

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🔄 Rebuild After Code Changes

If changes are made to services:

docker compose up -d --build

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📦 Dockerized Services

The system includes containerized versions of:

• API Gateway
• Eureka Discovery Server
• User Service
• Flight Inventory Service
• Booking Service
• Payment Service
• Notification Service
• Kafka + Zookeeper
• PostgreSQL
• Frontend (React + TypeScript)

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✅ Features Enabled in Dockerized Environment

• Service Discovery using Eureka
• Inter-service communication
• Kafka-based event processing
• JWT authentication
• Real-time booking workflow
• Persistent PostgreSQL storage
• Full microservices orchestration

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