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Atlassian·Software Engineer·Onsite - System Design / Architecture·Senior

Senior
Jun 2026

Summary

Atlassian system design round, rapid-fire format where they throw a scenario at you and expect you to just start talking through it methodically. Not a lot of back-and-forth, more like they're watching how your brain works under pressure.

Questions Asked (1)

Q1

A system starts slowing down noticeably after you scale it up by adding more nodes, replicas, or load. How do you troubleshoot it?

System DesignRoot Cause AnalysisTechnical Trade-offs
Author's notes

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AI HintsAI Generated

Suggested Approach

Start by acknowledging that scaling can introduce new bottlenecks and that a systematic, data-driven approach is key. Outline a structured troubleshooting process: gather metrics, identify the bottleneck, form hypotheses, and test them. Emphasize that the goal is to find the root cause, not just treat symptoms.

Pro tip: Mention that scaling often shifts bottlenecks to shared resources like databases or coordination services, so focus on those first. Also, highlight the importance of comparing performance before and after scaling to isolate the issue.

1. Gather Data and Metrics

Collect metrics from all layers (application, database, network, infrastructure) to understand where the slowdown occurs. Use monitoring tools to compare performance before and after scaling.

2. Identify the Bottleneck

Analyze the data to pinpoint the resource or component that is saturated or behaving abnormally. Look for increased latency, error rates, or resource utilization.

3. Form Hypotheses

Based on the bottleneck, hypothesize potential causes such as contention, increased coordination overhead, or inefficient load distribution.

4. Test and Validate

Design experiments or make targeted changes to test each hypothesis, such as adjusting configurations, adding caching, or optimizing queries. Measure the impact.

5. Implement and Monitor

Once the root cause is identified and fixed, implement the solution and continue monitoring to ensure the issue is resolved and no new bottlenecks appear.

Key Points to Mention

  • Amdahl's Law and the limitations of scaling
  • Database contention and locking
  • Network latency and bandwidth
  • Load balancer configuration and algorithms
  • Distributed system coordination overhead (e.g., consensus protocols)
  • Caching strategies and cache coherence

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.