Event Ticket Booking System

A Node.js application for managing event ticket bookings with concurrent request handling and waiting list management.

Features

• Event management (create, update, cancel)
• Ticket booking with automatic waiting list
• Concurrent booking handling
• Real-time ticket availability tracking
• Comprehensive error handling
• API rate limiting
• Request logging

Prerequisites

• Node.js >= 20.x
• MySQL >= 8.0
• yarn >= 1.x

Installation

1. Clone the repository:

git clone https://github.com/johnayinde/event-ticketing-system.git
cd event-ticketing-system

2. Install dependencies:

yarn install

3. Configure environment:

cp .env.example .env
# Edit .env with your configuration

4. Run migrations:

yarn run migrate

Running the Application

Development:

yarn run dev

Tests:

yarn run test

API Documentation

Initialize Event

POST /initialize
Content-Type: application/json

Request:
{
  "name": "Concert 2025",
  "totalTickets": 100
}

Response: (201 Created)
{
  "id": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
  "name": "Concert 2025",
  "totalTickets": 100,
  "availableTickets": 100,
  "status": "PUBLISHED"
}

Book Ticket

POST /book
Content-Type: application/json

Request:
{
  "eventId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
  "identifier": "user@example.com",
  "quantity": 1  // optional, defaults to 1
}

Response (Success): (201 Created)
{
  "tickets": [{
    "id": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "eventId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "userId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "status": "BOOKED"
  }],
  "waitlisted": false
}

Response (Waitlisted):
{
  "waitingEntry": {
    "id": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "eventId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "userId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "position": 1
  },
  "waitlisted": true
}

Cancel Ticket

POST /cancel
Content-Type: application/json

Request:
{
  "eventId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
  "identifier": "user@example.com"
}

Response: (200 OK)
{
  "ticket": {
    "id": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
    "status": "CANCELLED"
  }
}

Get Event Status

GET /status/:eventId

Response: (200 OK)
{
  "eventId": "6c2528c6-7b44-4274-97f4-d98ad525ea9f",
  "name": "Concert 2025",
  "totalTickets": 100,
  "availableTickets": 95,
  "waitingListCount": 2
}

Design Choices

Database Design

• Used UUID for primary keys to prevent sequential ID prediction
• Implemented proper indexing for frequent queries
• Used ENUM types for status fields to ensure data integrity

Concurrency Handling

• Implemented row-level locking to prevent race conditions
• Used SERIALIZABLE transaction isolation level for ticket bookings
• Added retry mechanism for handling deadlocks

Error Handling

• Comprehensive error handling with meaningful messages
• Transaction rollback on failures
• Proper HTTP status codes for different scenarios

Testing

• Unit tests for core business logic
• Integration tests for API endpoints
• Concurrent booking tests
• Database cleanup between tests