Design a Order Processing Service
Last updated: May 13, 2026
Quick Overview
Design a fault-tolerant order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Robinhood
May 13, 202621
9
3,771 solved
Design a fault-tolerant order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
This is a common system design question asked during System Design Round at Robinhood. The interviewer expects you to demonstrate your ability to design large-scale distributed systems, make well-reasoned trade-offs, and communicate your thought process clearly. Robinhood values engineers who can think about scalability from day one.
What the Interviewer Expects
- Clearly define functional and non-functional requirements
- Propose a reasonable high-level architecture with core components
- Choose appropriate data storage solutions with basic justification
- Discuss basic scaling strategies (horizontal scaling, caching)
- Identify potential bottlenecks and suggest simple solutions
Key Topics to Cover
How to Approach This
- Start by clarifying functional and non-functional requirements with the interviewer.
- Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
- Draw a high-level architecture first, then deep dive into 1-2 critical components.
- Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
- Address failure scenarios, monitoring, and how the system handles 10x traffic spikes.
Possible Follow-up Questions
- What monitoring and alerting would you set up on day one?
- How would you handle a region-wide outage?
- How would you implement rate limiting to protect the system?
- What happens if one of your database nodes goes down?
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Requirements
Functional Requirements:
- Order Placement: Users must be able to place buy/sell orders for stocks via REST API.
- Order Status: Users should be able to check the status of their orders....
Capacity Estimation
To estimate capacity, let’s assume Robinhood handles about 10 million users.
- Average Orders/User/Day: 3 orders
- Total Orders/Day: 10 million users * 3 orders = 30 million orders/day
- **Pea...
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