L8 · Hard
Payment Gateway
Problem
Design a payment processing system that handles transactions across multiple payment methods and providers.
Requirements
- Support payment methods: Credit Card, UPI, Net Banking, Wallet
- Process, refund, and capture transactions
- Idempotency for duplicate request protection
- Webhook notifications for payment status
- Fraud detection hooks
- Transaction history and reconciliation
Constraints
- –Each transaction must have unique idempotency key
- –Refund only possible within 30 days
- –PCI compliance: never store raw card data
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