Can you give an example of refactoring code to follow SRP?

Short answer: Before (SRP Violation): public class Invoice

Example code

{
public void GenerateInvoice() { /* logic */ }
public void SaveToDatabase() { /* logic */ }
public void SendEmail() { /* logic */ }
} This class has 3 responsibilities: generating, saving, and emailing. After (SRP-compliant): public class InvoiceGenerator
{
public void Generate() { /* logic */ }
}
public class InvoiceRepository
{
public void Save(Invoice invoice) { /* logic */ }
}
public class EmailService
{
public void Send(Invoice invoice) { /* logic */ }
} Now each class has a single reason to change.

Real-world example (ShopNest)

Open/Closed in ShopNest: add a new payment method by adding a class, not by editing a giant switch in CheckoutService.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.