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
System Design
Software Engineer
PayPal
June 9, 2026
Software Engineer
System Design Round
System Design
Easy

2

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
Model selection and architecture
Monitoring and model degradation detection
Online vs offline evaluation
ML objective formulation and metric selection
How to Approach This
  1. Start by clarifying functional and non-functional requirements with the interviewer.
  2. Estimate the scale: QPS, storage, bandwidth. This drives your design decisions.
  3. Draw a high-level architecture first, then deep dive into 1-2 critical components.
  4. Discuss trade-offs explicitly (e.g., consistency vs availability, SQL vs NoSQL).
  5. 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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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For multi-tenant Logging Pipeline, key functional requirements include: w...

Capacity Estimation

Estimate the scale to drive design decisions. Assume 100M DAU with an average of 10 actions per user per day = 1B requests/day ~ 12K QPS average, ~36K...


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