Low level design: Payment gateway system

Designing a Robust Payment Gateway System: Class Structure, Error Handling, and Transaction Rollback

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To design a payment gateway system that supports multiple payment modes like credit cards, PayPal, etc., we need a robust, flexible, and scalable class design.

Low level design diagram

LLD of Payment system

1. Class Design for Payment Methods
   We need a design that allows easy addition of new payment methods while maintaining clear separation of concerns. The Strategy Pattern works well here, where each payment method is encapsulated in its own class, following the same interface.

// Payment Interface
public interface Payment {
    boolean initiatePayment(double amount);
    boolean verifyPayment();
}

// CreditCardPayment
public class CreditCardPayment implements Payment {
    @Override
    public boolean initiatePayment(double amount) {
        // Logic to initiate credit card payment
    }

    @Override
    public boolean verifyPayment() {
        // Logic to verify payment
    }
}

// PayPalPayment
public class PayPalPayment implements Payment {
    @Override
    public boolean initiatePayment(double amount) {
        // Logic to initiate PayPal payment…