Crypto Wallet Backend API

Backend proxy service for fetching transaction history via Alchemy API. Keeps Alchemy API keys secure on the server side.

Setup

1. Install dependencies:

   cd backend
   npm install
   # or
   pnpm install

2. Configure environment variables:

   cp env.example .env

   Edit .env and add your Alchemy API keys:

   ALCHEMY_KEY_ETH=your_eth_mainnet_key_here
   ALCHEMY_KEY_BASE=your_base_mainnet_key_here
   ALCHEMY_KEY_ARB=your_arbitrum_mainnet_key_here
   ALCHEMY_KEY_POLY=your_polygon_mainnet_key_here

3. Build and run:

   # Development mode
   npm run start:dev
   
   # Production build
   npm run build
   npm run start:prod

The server will start on http://localhost:3000 (or the port specified in .env).

API Endpoints

GET /evm/:chainId/tx-history

Fetch transaction history for an address.

Parameters:

• chainId (path): Chain ID (1=Ethereum, 8453=Base, 42161=Arbitrum, 137=Polygon, etc.)
• address (query, required): Ethereum address (0x...)
• pageKey (query, optional): Pagination cursor from previous response
• pageSize (query, optional): Number of results per page (default: 100, max: 100)
• fromBlock (query, optional): Starting block (hex, default: 0x0)
• categories (query, optional): Comma-separated list (external,erc20,erc721,erc1155)

Example:

curl "http://localhost:3000/evm/1/tx-history?address=0xabc...&pageSize=20"

Response:

{
  "items": [
    {
      "hash": "0x...",
      "chainId": 1,
      "timestamp": "2026-01-13T02:14:11.000Z",
      "direction": "out",
      "assetType": "erc20",
      "from": "0xabc...",
      "to": "0xdef...",
      "value": "12.5",
      "symbol": "USDC",
      "tokenAddress": "0xA0b8..."
    }
  ],
  "nextPageKey": "..."
}

Features

• ✅ Rate Limiting: 60 requests/minute per IP
• ✅ Caching: In-memory cache (1 min for first page, 5 min for paginated)
• ✅ Input Validation: Address format, chainId, pageSize validation
• ✅ Error Handling: Comprehensive error messages
• ✅ Logging: Request logging with latency tracking

Supported Chains

• Ethereum Mainnet (1)
• Base (8453)
• Arbitrum (42161)
• Polygon (137)
• Sepolia Testnet (11155111)
• Base Sepolia (84532)

Mobile App Configuration

In your mobile app .env or app.json, set:

EXPO_PUBLIC_API_BASE_URL=http://localhost:3000

For production, use your deployed backend URL.