Design a Software Load Balancer
Last updated: August 14, 2026
Quick Overview
The question asks you to design a software load balancer, allowing you to choose between Layer 4 (L4) or Layer 7 (L7) load balancing.
Oracle
August 14, 20261
0
12 solved
The question asks you to design a software load balancer, allowing you to choose between Layer 4 (L4) or Layer 7 (L7) load balancing.
This question is commonly asked during onsite interviews for software engineering roles, particularly at Oracle, to evaluate a candidate's ability to design scalable and efficient systems. The interviewer is interested in understanding your thought process, technical knowledge, and ability to address real-world challenges related to load balancing, such as traffic distribution, fault tolerance, and performance optimization.
What the Interviewer Expects
- Clearly define the requirements for the load balancer, including performance and scalability needs.
- Choose between L4 and L7 load balancing and justify your choice.
- Provide a high-level architecture diagram and explain the components involved.
- Discuss the trade-offs associated with your design, including potential bottlenecks and scaling strategies.
- Consider security and fault tolerance in your design.
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 session persistence in your load balancer?
- What metrics would you monitor to ensure optimal performance?
- Can you explain how you would implement health checks for the backend servers?
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Practice System Design ProblemsSample Answer
Requirements
To design a software load balancer, we need to first establish the requirements. Key requirements include handling high traffic loads, ensuring low latency, and providing fault tolerance. Additionally...
High-Level Design
For this design, I will choose Layer 7 load balancing, which allows for more advanced routing based on application data. The high-level architecture includes:
- Client Requests: Clients send req...
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