Design a Feed Generation Service
Last updated: February 19, 2026
Quick Overview
Design a fault-tolerant feed generation system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
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Design a fault-tolerant feed generation system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Google asks this during the Onsite 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
- Define clear ML objectives with appropriate loss functions and metrics
- Design a comprehensive feature engineering pipeline
- Discuss model selection with trade-offs (complexity vs interpretability vs latency)
- Plan online and offline evaluation strategies including A/B testing
- Address serving infrastructure: batch vs real-time, latency requirements
- Consider data quality, labeling strategy, and feedback loops
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?
- What would you do if model performance degrades over time?
- How would you handle a 10x increase in prediction requests?
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Requirements
Functional Requirements
- User Feed Generation: The service should generate personalized feeds for users based on their interactions, preferences, and demographic data.
- **Real-time Updates...
Capacity Estimation
Capacity Estimation
Assuming Google has 1 billion active users and that each user requests a feed update every 30 seconds:
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Total Requests per Second:
[ ext{Total Requests} = rac{1,0...
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