Stock Trading Platform (Robinhood)
Difficulty: Hard
What It Tests
Low-latency data delivery, order execution, financial system consistency.
Topics Covered
- Real-time Updates
- Distributed Transactions & Idempotency
- Consistent Hashing
- Database Design: SQL vs NoSQL
- Caching
Hello Interview Breakdown
Read the full Hello Interview breakdown →
Video Walkthroughs
- System Design Interview: Design Robinhood (Ex-Google SWE) →
- Design Robinhood: System Design Interview (Senior FAANG Engineer) →
Approach Hints
- Stream real-time market data via WebSocket (Kafka → WebSocket servers)
- Order placement with idempotency keys and exactly-once processing
- Account balance updates as atomic transactions (optimistic locking)
- Persist order book in PostgreSQL with strong consistency; use CQRS — separate read models (portfolio view) from write models (order processing)