STRKpay

Inspiration

Traditional payment processors charge high fees (2-3%) and are inaccessible in many regions. I wanted to leverage Starknet's Layer 2 technology to create a simple, QR-code based payment system with near-zero transaction fees that any merchant can use without technical knowledge.

What it does

StarkPay enables merchants to accept cryptocurrency payments through QR codes. Merchants generate a QR code with payment details, customers scan and pay using their Starknet wallet (ArgentX or Braavos), and the system automatically verifies the transaction on-chain. Merchants keep 98% of payments (2% platform fee), with all transactions tracked in a dashboard.

How we built it

Frontend: Next.js 14 with Tailwind CSS

Backend: Node.js/Express.js with MongoDB for database

Blockchain: Integrated Starknet.js to interact with Layer 2 smart contracts via Alchemy RPC

Payment Flow: QR generation → Wallet payment → Blockchain verification → Merchant receives funds

Challenges we ran into

Amount Matching: Struggled matching blockchain transactions with pending payments due to formatting differences. Implemented multi-strategy matching with exact match, variations, and time-based proximity.

Accomplishments that we're proud of

Built a fully functional payment system processing real transactions on Starknet

Designed clean, responsive UI that works seamlessly on mobile and desktop

Successfully integrated multiple Starknet wallets (ArgentX, Braavos)

What we learned

Blockchain integration with Starknet.js and handling on-chain event parsing

QR code technology with expiration and reuse prevention

Web3 wallet integration and transaction signing flows

What's next for STRKpay

Built With

• cairo
• express.js
• mongodb
• next.js
• node.js
• starknet.js