PayLite

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💡 Inspiration

We wanted to make crypto payments as simple as scanning a QR code. Existing Web3 checkouts are often slow or confusing — especially for small vendors who just want to receive a quick Solana payment without writing smart contracts or setting up complicated APIs. So we built PayLite, a lightweight Solana QR checkout that anyone can deploy, even on a Raspberry Pi or a free VPS.

⚙️ What it does

PayLite lets a merchant instantly generate a Solana QR code that customers can scan and pay using the Phantom Wallet app.

Phantom Sign-In → merchants connect and verify ownership of their wallet.

Generate Checkout → choose an amount, click “Generate QR,” and get a shareable QR.

Scan & Pay → customers scan with Phantom’s in-app QR scanner; the wallet pre-fills the recipient address.

Auto Confirm + Audio Alert → PayLite polls the Solana Devnet for incoming transactions and plays a “payment received” sound when funds land.

Everything happens client-to-wallet — no custodial servers, no private keys.

🧱 How we built it

Frontend

HTML + Bootstrap 5 for responsive UI

Vanilla JavaScript (ES6) for Phantom Wallet connection & message signing

bs58.js for base58 encoding

HTML5 Audio for success notification

Backend

Python 3 / Flask 3.0 web server

Flask-CORS for cross-origin wallet requests

PyNaCl to verify Phantom-signed login messages

qrcode + Pillow to generate checkout QRs

requests to call Solana RPC (getSignaturesForAddress, getTransaction, etc.)

python-dotenv for environment configuration (MERCHANT_PUBLIC_KEY, SOLANA_RPC)

Blockchain

Solana Devnet RPC endpoint (with optional Helius/Alchemy/QuickNode fallback)

Simple in-memory order tracking (ORDERS dict) and session store

Extras

Auto-polling every 3 seconds until payment confirmed

Fallback merchant address from .env if Phantom not signed in

Deployable via Vultr Docker or any simple Flask server

🚧 Challenges we ran into

RPC Timeouts: Devnet endpoints sometimes hang for 20 + seconds, delaying confirmation. We added shorter timeouts and retries.

Phantom Scanner: Some QR formats (with amount pre-filled) triggered “Send Error”. We fixed this by using a clean solana:

URI.

Session Persistence: Keeping the Phantom login session active between routes required careful CORS and cookie handling.

Latency: Polling every 3 seconds while avoiding blocked threads took tuning of Flask’s request timeouts.

🏆 Accomplishments that we’re proud of

Built a fully working crypto checkout without any smart-contract code.

Integrated Sign-In With Solana securely using real signature verification.

Designed a clean, Bootstrap UI with real-time updates and success sound.

Debugged full stack (Flask ↔ Phantom ↔ Solana RPC) end-to-end in one weekend.

📚 What we learned

How Solana’s JSON-RPC works under the hood (getTransaction, getSignatureStatuses).

How Phantom Wallet handles message signing and QR URIs.

How to manage sessions and authentication without a traditional database.

How to make a lightweight blockchain dApp feel like a normal web checkout.

🚀 What's next for PayLite

Instant confirmations via webhooks or a Solana indexer (Helius, Shyft, SolanaFM).

Multi-token support (USDC-SPL, BONK, etc.).

Merchant dashboard to track sales history.

Mobile PWA version so sellers can generate checkouts directly on their phone.

Mainnet launch with on-chain analytics and NFT receipts.

Built With

• flask
• html
• javascript
• phantom-wallet
• python
• sol
• solana