Build a fault-tolerant Order Processing Pipeline
Last updated: September 4, 2025
Quick Overview
Design a fault-tolerant order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Redfin
System Design
Software Engineer
Redfin
September 4, 2025Software Engineer
Technical Screen
System Design
Medium
143
14
4,912 solved
Design a fault-tolerant order processing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
System design interviews at Redfin typically last 45-60 minutes. You are expected to drive the conversation, starting from requirements gathering through to a detailed architecture. The interviewer will evaluate your ability to handle ambiguity and make practical engineering decisions.
What the Interviewer Expects
- Systematically gather requirements and estimate capacity (QPS, storage, bandwidth)
- Design a scalable architecture with clear component responsibilities
- Make well-reasoned database and caching decisions with trade-off analysis
- Address consistency vs availability trade-offs specific to the use case
- Discuss partitioning strategy, replication, and data modeling
- Cover failure handling, monitoring, and alerting strategies
Key Topics to Cover
Monitoring, logging, and alerting
Failure handling and fault tolerance
Security and authentication
API design and rate limiting
Database selection and data modeling
Caching strategies (local, distributed, CDN)
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 implement rate limiting to protect the system?
- What monitoring and alerting would you set up on day one?
- How would you handle a 10x increase in traffic overnight?
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Requirements
- Functional Requirements:
- Process millions of orders per day with minimal latency.
- Ensure each order can be tracked and retried in case of failure.
- Implement a secure authentica...
Capacity Estimation
- Assuming Redfin processes approximately 10 million orders per day:
- QPS Calculation:
- 10 million orders/day = 10,000,000 / (24 * 60 * 60) = ~115.74 QPS
- Storage Requirement:...
- QPS Calculation:
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