Design a large-scale Load Balancing Platform

Last updated: April 18, 2026

Quick Overview

Design a fault-tolerant load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Lyft
System Design
Software Engineer
Lyft
April 18, 2026
Software Engineer
Technical Screen
System Design
Easy

22

8

1,393 solved


Design a fault-tolerant load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.

Lyft asks this during the Technical Screen 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
  • 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 serving and latency optimization
A/B testing and experimentation
Monitoring and model degradation detection
ML objective formulation and metric selection
Feature engineering and feature stores
Training pipeline and infrastructure
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 run A/B tests on different model versions?
  • How would you handle the cold start problem?
  • How would you handle a 10x increase in prediction requests?
  • What is your model retraining strategy?
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Sample Answer
Requirements Clarification

Before diving into the architecture, clarify the scope with the interviewer. For large-scale Load Balancing Platform, key functional requirements incl...

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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