Design a Order Processing for Meta
Last updated: April 7, 2026
Quick Overview
Design a real-time order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Meta
April 7, 202610
14
4,584 solved
Design a real-time order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Meta asks this during the System Design Round to assess your understanding of the full ML lifecycle. They want to see how you translate a business problem into an ML objective, design the feature pipeline, and plan for model monitoring and retraining.
What the Interviewer Expects
- Map the business problem to a concrete ML objective
- Propose reasonable features and a baseline model
- Discuss basic model evaluation metrics
- Outline a simple serving architecture
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
- How would you ensure fairness and reduce bias in the model?
- How would you debug a model that works well offline but poorly online?
- How would you run A/B tests on different model versions?
- How would you handle the cold start problem?
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Requirements
Functional Requirements
- Real-time Order Processing: System must handle order placements, updates, and cancellations in real-time.
- User Notifications: Notify users of order status chang...
Capacity Estimation
Assuming Meta has around 2 billion active users and a 5% order placement rate:
- Daily Orders: 2B * 5% = 100M orders/day.
- Peak Load: Assuming 10% of daily orders come during peak hours, we h...
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