Design a supermarket checkout system

Q: Design a supermarket checkout system

This question evaluates system design competencies including domain modeling, API and service boundary definition, stateful session lifecycle, pricing and promotions modeling, and transactional consistency for point-of-sale workflows.

Q: How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

Question

Design the software for a supermarket checkout system.

A grocery store has multiple checkout lanes operated by cashiers, and the design should also be extensible to self-checkout. Customers bring items to a register, where the cashier scans products and the system computes the final total.

The system should support:

product lookup by barcode or PLU code
unit-based and weight-based items
quantities for the same item
taxes, discounts, promotions, and coupons
a running subtotal while items are scanned
voiding an item before payment
multiple payment methods such as cash and card
receipt generation
opening and closing a register session for a cashier

Discuss:

the core objects/classes and their responsibilities
the main APIs or service boundaries
the checkout session lifecycle and state transitions
how pricing and promotions should be modeled cleanly
error handling and data consistency concerns
how to extend the design later for loyalty programs, returns, and split payments

Design a supermarket checkout system

Quick Overview

Solution

Comments (0)