Pulend Backend

Professional Express backend service with Redis caching for fetching token prices from the TokenDataStream smart contract.

Features

• 🚀 Express.js REST API
• 💾 Redis caching with configurable TTL
• ⛓️ Blockchain integration via viem
• 🔒 Security middleware (Helmet, CORS)
• 📝 Request logging with Morgan
• ✅ Health check endpoints
• 🎯 TypeScript with strict type checking
• 🏗️ Professional code structure using functions

Prerequisites

• Node.js >= 18
• Redis server running
• RPC endpoint for blockchain access

Installation

# Install dependencies
npm install

# Copy environment variables
cp .env.example .env

# Edit .env with your configuration

Configuration

Edit .env file with your settings:

PORT=3001
NODE_ENV=development
RPC_URL=https://rpc.testnet.autonomys.xyz
CHAIN_ID=1315
REDIS_HOST=localhost
REDIS_PORT=6379
PRICE_CACHE_TTL=60

Development

# Run in development mode with hot reload
npm run dev

Production

# Build TypeScript
npm run build

# Start production server
npm start

API Endpoints

Health Check

GET /api/health

Returns the health status of Redis and blockchain connections.

Get All Token Prices

GET /api/prices

Optional query parameters:

• cache=false - Bypass cache and fetch fresh data

Example response:

{
  "success": true,
  "data": {
    "prices": [
      {
        "symbol": "IDRX",
        "name": "Indonesian Rupiah Token",
        "address": "0x056620afe01E33802ce50637438677Dc7b4841E0",
        "price": "0.000065",
        "priceRaw": "65000000000000",
        "decimals": 18,
        "updatedAt": 1701234567,
        "roundId": "1"
      }
    ],
    "timestamp": 1701234567890,
    "cached": true
  }
}

Get Price by Symbol

GET /api/prices/:symbol

Example:

GET /api/prices/weth

Refresh All Prices

POST /api/prices/refresh

Forces a refresh of all prices, bypassing the cache.

Project Structure

backend/
├── src/
│   ├── config/          # Configuration files
│   │   ├── abi.ts       # Contract ABI
│   │   ├── constants.ts # Contract addresses & metadata
│   │   └── env.ts       # Environment variables
│   ├── middleware/      # Express middleware
│   │   └── error.middleware.ts
│   ├── routes/          # API routes
│   │   ├── health.routes.ts
│   │   └── price.routes.ts
│   ├── services/        # Business logic
│   │   ├── blockchain.service.ts
│   │   ├── price.service.ts
│   │   └── redis.service.ts
│   ├── app.ts          # Express app setup
│   └── index.ts        # Entry point
├── .env.example        # Environment template
├── package.json
├── tsconfig.json
└── README.md

Architecture

The backend follows a layered architecture with clear separation of concerns:

1. Routes Layer: Handle HTTP requests and responses
2. Service Layer: Business logic and orchestration
3. Infrastructure Layer: External service interactions (Redis, Blockchain)

Key Services

• Redis Service: Manages caching operations
• Blockchain Service: Interacts with smart contracts
• Price Service: Orchestrates price fetching with caching logic

Caching Strategy

• Token prices are cached in Redis with configurable TTL (default: 60 seconds)
• Cache keys follow the pattern: price:{symbol}
• Cache can be bypassed by adding ?cache=false to requests
• Use /api/prices/refresh to force a cache refresh for all tokens

Error Handling

All errors are handled consistently and return JSON responses:

{
  "success": false,
  "error": "Error message",
  "stack": "Stack trace (development only)"
}

Security

• Helmet.js for security headers
• CORS configuration
• Input validation
• Error stack traces only in development

License

MIT