You have 90 seconds to verbally explain how you would design a real-time stock ticker and trading platform like Robinhood or E*TRADE.
Your system should: - Display live stock prices updated every second - Handle 10 million concurrent users - Execute trades with sub-second latency - Ensure no user sees stale prices when placing orders - Provide order history and portfolio tracking
Explain your architecture, data streaming, and consistency guarantees.
How to approach it
- Hint 1
Use WebSocket or Server-Sent Events to push real-time price updates to clients
- Hint 2
Separate read path (price display) from write path (order execution) with CQRS pattern
- Hint 3
Ensure read-after-write consistency - user sees their own order immediately
Ready to answer it out loud?
Record your answer in 1:30 and Preptile scores it 1–10 with specifics — what landed, what you skipped, and what to say next time.
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