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Scalable Ticket Management Solution

A high-performance, cost-optimized ticket booking system designed to handle massive concurrent traffic during concert releases. Built with serverless architecture and modern cloud-native patterns. Inspired by ticketmaster

What is the problem?

Traditional ticket booking systems face critical challenges during high-demand events:

  • High Concurrency: Thousands of users competing for limited tickets simultaneously
  • Race Conditions: Multiple users attempting to purchase the same seat at the same time
  • Cost Optimization: Need to scale efficiently without over-provisioning as a lot of people is using the system
  • Performance: Sub-second response times during peak traffic

Architecture Overview

Core Architecture Principles

  • Serverless-First: Auto-scaling Lambda functions for unpredictable traffic patterns
  • Event-Driven: EventBridge for orchestration and Lambda warming
  • Cache-Heavy: Redis/ElastiCache for temporary seat reservations
  • Database Optimization: DynamoDB for single-key lookups and to aid for massive scale
  • Idempotency: Ensuring safe retries and preventing duplicate purchases

High-Level Architecture

┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
│  React Frontend │────│   API Gateway    │────│ Lambda Functions│
│  User Interface │    │   (Rate Limiting)│    │ (Business Logic)│
└─────────────────┘    └──────────────────┘    └─────────────────┘
                                                       │
                       ┌──────────────────┐            │
                       │   EventBridge    │────────────┘
                       │   (Orchestration)│
                       └──────────────────┘
                                │
┌─────────────────┐    ┌──────────────────┐    ┌─────────────────┐
│   DynamoDB      │────│   ElastiCache    │────│   State Machine │
│   (Persistent)  │    │   (Reservations) │    │   (Workflow)    │
└─────────────────┘    └──────────────────┘    └─────────────────┘

Key Features

User Journey

  1. Authentication: Secure login/signup with JWT tokens
  2. Concert Selection: Browse and filter available concerts
  3. Seat Selection: Real-time seat availability fetched from Redis - users can only click available seats
  4. Checkout Process: Stripe payment processing with seat reservation
  5. Account Management: View purchased tickets and booking history

Concurrency Solutions

  • Seat Reservation System: 5-minute TTL in Redis for checkout process
  • Exponential Backoff: Retry mechanisms for failed operations
  • State Machine: Orchestrated workflow for ticket purchase lifecycle
  • Idempotency Keys: Prevent duplicate transactions
  • Lambda Warming: Pre-provisioned capacity for known high-traffic events

Tech Stack

Frontend

  • React with TypeScript
  • Tailwind CSS for styling
  • React Query for state management and caching

Backend

  • NestJS with TypeScript
  • TypeORM for database ORM with PostgreSQL
  • class-validator for request validation
  • Swagger for API documentation
  • JWT for authentication
  • Redis for seat reservation caching
  • Stripe for payment processing
  • AWS Lambda for serverless functions (production)
  • API Gateway for request routing and rate limiting (production)
  • EventBridge for event orchestration (production)

Database & Caching

  • DynamoDB for persistent data storage
  • ElastiCache (Redis) for temporary seat reservations and real-time seat availability
  • Local Development: MongoDB/Redis for development (NoSQL to match production)

Infrastructure

  • Terraform for Infrastructure as Code
  • Docker for local development
  • GitHub Actions for CI/CD pipeline

AWS Services

  • Lambda: Serverless compute
  • API Gateway: API management
  • DynamoDB: NoSQL database
  • ElastiCache: Redis caching
  • EventBridge: Event routing and warming up of lambdas
  • CloudWatch: Monitoring and logging
  • CloudFront: CDN for global distribution

Concurrency Handling Strategy

Seat Reservation Flow

1. User views seats → Fetch availability from Redis (real-time)
2. User clicks available seat → Reserve in Redis (5min TTL)
3. User proceeds to checkout → Validate reservation
4. Stripe payment success → Move from Redis to DynamoDB
5. Payment failure/timeout → Release reservation

Data Consistency Strategy

  • Eventual Consistency: Redis serves as the source of truth for seat availability
  • Strong Consistency: DynamoDB conditional writes ensure no double-booking
  • Sync Mechanism: Background jobs sync Redis with DynamoDB changes
  • Conflict Resolution: Last-write-wins with timestamp-based versioning

Race Condition Prevention

  • Optimistic Locking: Version fields in DynamoDB
  • Atomic Operations: Conditional writes with existence checks
  • Distributed Locks: Redis-based locking mechanism
  • Circuit Breaker: Prevent cascade failures

Performance Optimizations

Caching Strategy

  • Redis Cache: Real-time seat availability and temporary reservations
  • Lambda Memory: In-memory caching for concert metadata and static data
  • DynamoDB: Persistent storage with eventual consistency sync to Redis

Scaling Patterns

  • Horizontal Scaling: Auto-scaling Lambda functions
  • Vertical Scaling: Provisioned capacity for known events
  • Geographic Distribution: Multi-region deployment
  • CDN: CloudFront for static assets

Cost Optimization

  • Pay-per-request: DynamoDB on-demand billing
  • Spot Instances: For non-critical workloads
  • Reserved Capacity: For predictable traffic patterns
  • Auto-scaling: Right-size resources based on demand

Development Setup

Prerequisites

  • Node.js 18+
  • Docker & Docker Compose
  • AWS CLI configured
  • Terraform 1.0+

Local Development

# Clone repository
git clone <repository-url>
cd ticket-management-system

# Start local services
docker-compose -f docker-compose-dev.yml up -d

# Install dependencies
cd backend && npm install
cd ../frontend && npm install

# Start development servers
cd backend && npm run start:dev
cd frontend && npm run dev

Deployment

Infrastructure Deployment

cd iac
terraform init
terraform plan
terraform apply

Thoughts and Reflections

After researching how ticketmaster handle extreme traffic, i discovered that Ticketmaster likely uses Cloudflare Workers and Cloudflare virtual waiting rooms to manage massive concurrent demand. While this current proposed solution provides a solid foundation for handling high concurrency, it may still face challenges during unprecedented events like Taylor Swift concerts where demand can exceed millions of concurrent users. However, its a good start and there is room for improvement.

Key Limitations Identified:

  • Scale Ceiling: Even with auto-scaling Lambda functions, AWS has concurrency limits
  • Cold Start Latency: Lambda cold starts could impact user experience during traffic spikes
  • Redis Bottleneck: Single Redis instance could become a bottleneck at extreme scale

About

A scalable ticket management system designed to handle high concurrency events and provide fair access to users | Terraform | Lambda | EventBridge | Redis | High Concurrency

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