⚡ GasLance

Gas Price Sniper for Smart Contract Deployments

Deploy your smart contracts when gas prices drop. GasLance monitors Ethereum gas prices 24/7 and broadcasts your pre-signed transactions automatically.

Features • Architecture • Quick Start • API Docs • Deployment

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✨ Features

Feature	Description
🔐 Non-custodial	We never hold your private keys. You sign transactions locally.
⛽ Gas Sniping	Set a target gas price and we'll broadcast when conditions match
📊 EIP-1559 Compatible	Full support for modern Ethereum transactions
💳 Credit System	Pay-per-deployment with Stripe integration
🌐 Multi-chain	Supports Mainnet, Sepolia, and more
📚 OpenAPI Docs	Interactive Swagger documentation at /api/docs

🏗 Architecture

flowchart TB
    subgraph Frontend["Frontend (Next.js)"]
        UI[Dashboard UI]
        Wallet[Wagmi Wallet]
    end

    subgraph Backend["Backend (NestJS)"]
        API[REST API]
        Watcher[Gas Watcher]
        Payment[Payment Service]
        DB[(PostgreSQL)]
    end

    subgraph External["External Services"]
        RPC[Ethereum RPC]
        Stripe[Stripe]
    end

    UI --> |Sign Tx| Wallet
    Wallet --> |Submit Order| API
    API --> |Store| DB
    Watcher --> |Monitor Gas| RPC
    Watcher --> |Broadcast Tx| RPC
    Watcher --> |Check Orders| DB
    UI --> |Buy Credits| Payment
    Payment --> |Checkout| Stripe
    Stripe --> |Webhook| Payment

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🔄 How It Works

sequenceDiagram
    participant User
    participant Frontend
    participant Backend
    participant Ethereum

    User->>Frontend: Connect Wallet
    User->>Frontend: Configure Deployment
    Frontend->>User: Request Signature
    User->>Frontend: Sign Transaction
    Frontend->>Backend: Submit Order
    Backend->>Backend: Validate & Store
    
    loop Every 12 seconds
        Backend->>Ethereum: Check Gas Price
        alt Gas Price ≤ Target
            Backend->>Ethereum: Broadcast Tx
            Backend->>Backend: Update Order Status
        end
    end

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🚀 Quick Start

Prerequisites

• Node.js 20+
• Docker & Docker Compose
• Ethereum RPC (Alchemy, Infura, or Ankr)
• Stripe account (for payments)

Development Setup

# 1. Start database
docker compose -f docker-compose.dev.yml up -d

# 2. Setup backend
cd backend
cp .env.example .env  # Edit with your API keys
npm install
npx prisma migrate dev
npm run start:dev

# 3. Setup frontend (new terminal)
cd frontend
cp .env.example .env
npm install
npm run dev

Environment Variables

Backend (.env)

# Database
DATABASE_URL=postgresql://gaslance:gaslance_dev_password@localhost:5439/gaslance

# Server
PORT=3001
FRONTEND_URL=http://localhost:3000

# Ethereum RPC
MAINNET_RPC_URL=https://eth-mainnet.g.alchemy.com/v2/YOUR_KEY
SEPOLIA_RPC_URL=https://eth-sepolia.g.alchemy.com/v2/YOUR_KEY

# Stripe
STRIPE_SECRET_KEY=sk_test_xxx
STRIPE_WEBHOOK_SECRET=whsec_xxx

📚 API Documentation

Interactive API docs are available at:

http://localhost:3001/api/docs

Key Endpoints

Method	Endpoint	Description
GET	/health	Health check with DB status
POST	/sniper	Create deployment order
GET	/sniper/user/:userId	Get user's orders
GET	/sniper/credits/:userId	Check credit balance
GET	/payment/packages	List credit packages
POST	/payment/checkout	Create Stripe session

💰 Credit System

Package	Credits	Price	Savings
Starter	5	$5	—
Pro	15	$12	20%
Power	50	$35	30%

New users receive 1 free credit to try the service.

🐳 Deployment

Docker Compose (Production)

# Set environment variables
export MAINNET_RPC_URL=your_url
export STRIPE_SECRET_KEY=sk_live_xxx

# Build and deploy
docker compose up -d --build

# Run migrations
docker compose exec backend npx prisma migrate deploy

Services

Service	Port	Description
frontend	3000	Next.js web app
backend	3001	NestJS API
postgres	5432	PostgreSQL database

📁 Project Structure

gaslance-api/
├── backend/                 # NestJS API
│   ├── src/
│   │   ├── sniper/          # Order management
│   │   ├── watcher/         # Gas monitoring & broadcasting
│   │   ├── payment/         # Stripe integration
│   │   └── prisma/          # Database service
│   └── prisma/              # Schema & migrations
├── frontend/                # Next.js app
│   └── src/
│       ├── app/             # Pages (App Router)
│       └── components/      # React components
├── .github/workflows/       # CI/CD pipelines
├── docker-compose.yml       # Production deployment
└── docker-compose.dev.yml   # Development (DB only)

🔒 Security

• ✅ Non-custodial: Users sign transactions locally
• ✅ Input validation: class-validator on all DTOs
• ✅ Webhook verification: Stripe signature validation
• ✅ CORS: Restricted to frontend origin
• ✅ Address normalization: All addresses lowercased

🛠 Tech Stack

Layer	Technology
Frontend	Next.js 15, React 18, TypeScript, Wagmi, Viem
Backend	NestJS 11, Prisma, TypeScript
Database	PostgreSQL 16
Payments	Stripe Checkout
DevOps	Docker, GitHub Actions

📝 License

MIT © 2026

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_{Built with ❤️ for the Ethereum community}