Build a multi-tenant Logging Pipeline
Last updated: June 9, 2026
Quick Overview
Design a multi-tenant logging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
PayPal
June 9, 20262
5
2,081 solved
Design a multi-tenant logging system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
ML system design at PayPal goes beyond model selection. This System Design Round question evaluates your ability to design end-to-end ML pipelines, from data collection to model serving, while considering production constraints like latency and reliability.
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?
- What would you do if model performance degrades over time?
- How would you handle the cold start problem?
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Requirements
Functional Requirements
- Multi-Tenancy Support: The system must isolate logging data per tenant to ensure data privacy and compliance.
- Log Ingestion: Support for high-throughput log i...
Capacity Estimation
Assuming PayPal processes approximately 1 billion transactions a day. If each transaction generates an average of 5 log entries:
- Total Logs Daily: 1 billion transactions * 5 logs = 5 billion log...
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