Design
Online Shopping Cart
Design an e-commerce shopping cart system supporting product catalogue, cart management, promotions, checkout, and order tracking.
This is a Low-Level Design (LLD) problem. New to LLD vs HLD? Start here.
01 - Why interviewers ask this
It's a deceptively rich e-commerce problem — interviewers watch for whether pricing/promotion rules are cleanly pluggable (Strategy/Decorator) rather than hardcoded into the cart itself.
02 - Where this system exists in the real world
You interact with this design every day.
Amazon / Shopify-style e-commerce carts
Grocery delivery app checkout flows
B2B ordering platforms with tiered pricing
03 - What you'll master
Solve this once. Know it forever.
Model cart line items, quantities, and pricing
Apply Strategy/Decorator for promotions
Handle inventory checks at checkout time
04 - What you'll design
7 functional · 4 non-functional requirements.
Browse and search the product catalog with filters
6 more requirements inside
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05 - Companies that ask this
You may face this exact question in your next interview.
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