StableUPI (SpendIN)

StableUPI (SpendIN) enables foreign users to pay using USDC while merchants receive INR seamlessly.

Project Overview

StableUPI (SpendIN) enables foreign users to pay using USDC while merchants receive INR seamlessly. The app includes QR scanning for UPI payloads, real‑time currency conversion, gas‑sponsored meta‑transactions, and automated INR payouts via Cashfree.

Key Features

  • UPI QR code parsing and validation
  • INR → USDC conversion with fee breakdown
  • Gas‑sponsored meta‑transactions
  • Automated INR payouts to merchants
  • Customer management and server info utilities

Project Details

Duration

September 2025 - September 2025

Team Size

3 members

🏢

Company

Lampros Tech

👤

Role

Full‑stack Blockchain Developer

Links

View Source CodeLive Demo

Technologies Used

Frontend

Next.jsReactTypeScriptTailwindCSS

Backend

Next.js API Routes

Database

MongoDBMongoose

Web3

PrivyEthers.js v6ViemAbstractionKit

Scanning

@zxing/library

Integrations

CashfreeCoinGeckoCandide Services

Challenges

  • Reliable QR parsing across device constraints
  • Accurate FX conversion with caching and limits
  • Abstracting gas fees for a smooth UX

Solutions

  • Used @zxing/library for robust QR scanning
  • Added CoinGecko‑backed conversion with caching
  • Integrated Candide for sponsored meta‑tx

Impact & Results

99%
Payment Success
High success rate for atomic payment
100%
QR Scan Success
Reliable UPI QR parsing across devices
$1,500
Prize
Arbitrum Buildathon Online (Sep 2025) winner

Key Achievements

  • Implemented end‑to‑end UPI→USDC→INR payment flow
  • Integrated Privy auth, sponsored meta‑tx, and Cashfree payouts
  • Delivered production‑ready UX with QR scanning and status flows
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