Ticketmain (High-Concurrency Ticket Engine)

The Challenge: In a standard web app, two users clicking "Buy" at the same time is fairly rare. In a ticket launch, it's guaranteed to happen. This project implements a distributed locking mechanism to prevent race conditions and "double bookings" when thousands of concurrent requests target the same inventory.

🛠️ Tech Stack & Architecture

• Frontend: React (Vite + TypeScript) with Optimistic UI updates
• Backend: Go (Fiber) for high-performance HTTP & WebSocket handling
• State Management: Redis (for atomic SET NX locking and real-time pub/sub)
• Persistence: PostgreSQL (for ACID-compliant transaction recording)
• Infrastructure: Docker & Docker Compose

⚡️ Key Features

• Real-Time Seat Map: WebSocket integration pushes seat status updates (Held/Sold) to all connected users instantly
• Atomic Locking: Uses Redis Lua scripts to ensure hold/release operations are atomic and race-condition free
• Ephemeral Identity: Client-side UUID generation to simulate unique users without complex auth guardrails
• Performance: Utilizes Redis Pipelining to batch fetch thousands of seat states in a single network roundtrip

📦 Installation & Setup

Follow these steps to run the system locally.

1. Prerequisites:

• Docker Desktop (Running)
• Go (v1.21 or higher)
• Node.js (v18 or higher)

2. Start Infrastructure

Create the Redis and PostgreSQL containers.

# From root directory
docker-compose up -d

3. Start the Backend (Go)

This runs the API server at http://localhost:3000. The application will automatically create the necessary database tables on startup.

cd server
go mod tidy
go run main.go

You should see: ✅ Connected to Redis and ✅ Connected to Postgres and ensured table exists.

4. Start the Frontend (React)

This runs the UI at http://localhost:5173.

# Open a new terminal
cd client
npm install
npm run dev

🧪 How to Test Concurrency

1. Open the app in Chrome (or any other browser of your choice)
2. Open the app in Firefox (an incognito window, or any other browser of your choice)
3. Notice that you'll have a different User: user_xyz ID in each window
4. Click a seat in Chrome (first window)

• Result: Instant update in Firefox (second window, turns grey)

5. Try to click the same seat in Firefox (second window)

• Result: "Seat already held by another user" error.