Design a low-latency Load Balancing System
Last updated: April 16, 2026
Quick Overview
Design a low-latency load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Salesforce
April 16, 2026311
13
922 solved
Design a low-latency load balancing system that handles millions of requests. Discuss trade-offs in consistency, availability, and performance.
Salesforce 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 run A/B tests on different model versions?
- What is your model retraining strategy?
- How would you ensure fairness and reduce bias in the model?
- What would you do if model performance degrades over time?
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Requirements
Functional Requirements
- Request Routing: Distribute incoming requests across multiple servers to ensure low-latency responses.
- Health Checks: Regularly check the health of backend se...
Capacity Estimation
To estimate capacity, consider the following assumptions:
- Peak Requests: 1 million requests per minute.
- Average Response Time: 50 ms.
- Total Requests: 1,000,000 / 60 seconds = ~16,667...
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