# BUSINESS PLAN: SELF-HOSTED NON-CUSTODIAL CRYPTO PAYMENT GATEWAY

## 1. PROJECT OVERVIEW
A lightweight, open-source-inspired, non-custodial crypto payment gateway clone of Aurpay. It derives sequential merchant addresses via extended public keys, processes checkouts on a low-cost server, and takes a 0.8% transaction fee split on-the-fly directly at the blockchain level.

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## 2. INFRASTRUCTURE & MONTHLY BUDGET
* Server Hosting: $8.00 / month (1-2 GB RAM, 1 vCPU Virtual Private Server via DigitalOcean, Vultr, or Hetzner).
* Blockchain Data (RPC/APIs): $0.00 (Using free tiers from Infura, Alchemy, or BlastAPI).
* SSL Encryption: $0.00 (Free via Let's Encrypt / Certbot).
* Domain Name: ~$1.00 / month ($12/year renewal).
* TOTAL RUNNING COST: ~$9.00 / Month

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## 3. CORE ARCHITECTURE & CODE LOGIC

### A. Non-Custodial Address Generation (BIP32 / BIP44)
1. Merchant inputs their Extended Public Key (xpub for Bitcoin, or Account Extended Public Key for EVM chains) into your dashboard during setup.
2. The database assigns an `address_index` starting at `0` for that merchant.
3. Upon checkout, your backend runs a derivation function to generate a fresh public address:
   `Address = DerivationFunction(xpub, address_index)`
4. The database counter increments by 1 (`index++`) for the next invoice.
5. Absolute Security: Your server never holds private keys. If the server is hacked, zero funds can be stolen.

### B. Lightweight Tech Stack
* Backend: Node.js, Python (FastAPI), or Go.
* Database: SQLite or PostgreSQL (keeps RAM utilization below 200MB).
* Data Fetching: Queries external public APIs to monitor addresses rather than running hardware-heavy full nodes.

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## 4. REVENUE MODEL (THE 0.8% FEE SPLIT)
To replicate Aurpay without requiring merchants to deposit pre-paid gas balances, the 0.8% processing fee is split directly at the point of transaction authorization.

### Implementation Methods:
* UTXO Chains (Bitcoin): Code your payment URI/QR code generation to use BIP21 multi-output formats. A single user payment natively broadcasts two outputs simultaneously:
  * Output 1: 99.2% of the payment goes straight to the merchant's derived address.
  * Output 2: 0.8% of the payment goes straight to your gateway wallet address.
* Smart Contract Chains (Solana, Arbitrum, Tron): Your frontend Web3 checkout wrapper triggers an atomic split instruction inside the token contract execution:
  `USDT.transfer(merchantAddress, ninety_nine_point_two_percent);`
  `USDT.transfer(myGatewayWalletAddress, zero_point_eight_percent);`

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## 5. ARCHITECTURAL RISKS & MITIGATIONS
* High Gas Fee Chains: Splitting small transactions on mainnet Ethereum (ERC-20) can burn more in network gas fees than the 0.8% fee is actually worth.
* Mitigation Strategy: Code your gateway to exclusively enforce or incentivize low-fee rails: Bitcoin Lightning Network, Solana, Tron (TRC-20), and Ethereum Layer 2s (Arbitrum, Optimism). Waive or put a minimum threshold cap on high-fee layer-1 transfers.