Architect a multi-tenant Logging Engine
Last updated: December 10, 2025
Quick Overview
Design a multi-tenant logging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Waymo
December 10, 202532
6
1,220 solved
Design a multi-tenant logging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Waymo 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
- Design the full ML lifecycle from data collection to model monitoring
- Address cold start, exploration/exploitation, and model freshness
- Discuss multi-objective optimization and ranking systems
- Plan for model debugging, fairness, and bias mitigation
- Design the feature store and training pipeline for scale
- Address model versioning, canary deployments, and rollback strategies
- Discuss the data flywheel and long-term system evolution
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 handle the cold start problem?
- How would you ensure fairness and reduce bias in the model?
- How would you handle a 10x increase in prediction requests?
- How would you debug a model that works well offline but poorly online?
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Requirements
Functional Requirements:
- Multi-Tenant Support: The system must segregate logs from different tenants while allowing shared access to aggregate metrics.
- Real-Time Ingestion: The loggi...
Capacity Estimation
Assuming Waymo expects to handle 10 million logs per second during peak usage:
- Each log entry is approximately 1 KB.
- Daily logs: 10M logs/s * 60s * 60m * 24h = 864 billion logs/day.
- Daily data ...
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