What to work through
Work through a shopping site, from the listing to the cart as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- Browse a listing of products, filter and sort it, and come back to or share the same view
- Open a product page with its photos, its options such as size, its price and its stock
- Add to a cart, change quantities and remove items, as a guest or signed in
- Keep the cart when the tab closes and the shopper comes back later
Constraints to discuss
- The main content shows within 2.5 seconds on a phone, at the 75th percentile
- A tap answers within 200 milliseconds
- Listing and product pages can be read by search engines
- Layout shift stays at 0.1 or less while images load
- Usable with a keyboard and a screen reader
Need a starting point?
Watch for these common gaps as you prepare:
- Filters kept only in component state, so Back, a refresh and a shared link lose them
- A history entry for every filter click
- Blanking the result list while new results load
- Lazy-loading the first product image, or marking every image high priority
- Sending the cart total from the browser instead of letting the server price the cart
- Leaving search engines out of the design
Why this question is in the collection
These sources connect the problem to company interview reports or preparation guides. They do not guarantee what a company will ask you.
- eBay: A frontend candidate's July 2026 tip: the architecture round was designing eBay's journey from the listing page to the product page. The handbook's own notes, not the tip, add filters surviving a return and slow or failed product loads.
- Disney: A Lead Software Engineer (Frontend) candidate reports two whiteboard frontend design rounds at a Seattle onsite in November 2025; the first was a shopping cart.
- Atlassian: A senior frontend candidate reports a technical screen in October 2026: a search input over a product catalog grid with no limit on results, and how to keep results and filtering fast.
- Amazon: The Front End Interview Handbook lists a restaurant listing app where people order and customize their orders, from a candidate's April 2022 Frontend Engineer II virtual onsite post on LeetCode; that post could not be opened.