Architect a real-time Load Balancing Engine

Last updated: March 21, 2026

Quick Overview

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

Atlassian
System Design
Software Engineer
Atlassian
March 21, 2026
Software Engineer
Onsite
System Design
Easy

81

7

3,779 solved


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

Atlassian asks this during the Onsite to assess your architectural thinking. They want to see how you decompose a complex problem, choose appropriate technologies, and reason about failure modes. Strong candidates proactively discuss monitoring, alerting, and operational concerns.

What the Interviewer Expects
  • Clearly define functional and non-functional requirements
  • Propose a reasonable high-level architecture with core components
  • Choose appropriate data storage solutions with basic justification
  • Discuss basic scaling strategies (horizontal scaling, caching)
  • Identify potential bottlenecks and suggest simple solutions
Key Topics to Cover
Caching strategies (local, distributed, CDN)
High-level architecture and component design
Message queues and async processing
Failure handling and fault tolerance
Security and authentication
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
  • What happens if one of your database nodes goes down?
  • How would you migrate from a monolithic to a microservices architecture?
  • How would you handle schema migrations with zero downtime?
  • How would you handle a 10x increase in traffic overnight?
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Sample Answer
Requirements

Functional Requirements

  1. Load Balancing: Distribute incoming requests evenly across multiple application servers to ensure optimal resource utilization.
  2. Real-Time Metrics: Monitor the...
Capacity Estimation

Assuming Atlassian expects to handle approximately 100 million requests per day, we can break this down:

  • Requests per second: 100 million requests / 86400 seconds ≈ 1157 requests/second.
  • **Pea...

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