What to work through
Work through a trading screen as a spoken system design interview. Start by clarifying the scope, sketch a working design and explain the trade-offs behind your choices.
- Show a price chart, a live order book and recent trades for one market
- Place a market or limit order and see it go from sent to open to filled
- Show the person's open orders and holdings, kept up to date
- Show clearly when prices are stale or the live feed is down
Constraints to discuss
- Each frame's work fits in about 10 milliseconds, so the screen never stutters
- A tap on buy or sell answers within 200 milliseconds
- An order is never placed twice, however many times the button is pressed
- A price on screen is never older than it looks
Need a starting point?
Watch for these common gaps as you prepare:
- Redrawing the book on every message that arrives
- Showing a fill or a new balance before the exchange confirms it
- Retrying an order with no id that lets the exchange spot a repeat
- Showing old prices as live while the feed is down
- Ordering book changes by time instead of by sequence number
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.
- Coinbase: A staff frontend candidate reports an onsite round in early 2026, published in August 2026: the interviewer showed a screenshot of a trading UI and asked for its frontend architecture (state, error handling, loading, performance and security), then follow-up questions. The candidate was rejected and thinks this was the round they failed.
- Coinbase: Listed by PracHub on 2026-02-23 as a software engineer onsite question, with no candidate narrative: the frontend of a crypto trading web app with a price chart, a live order book, recent trades, an order form and a portfolio.