Systematic Troubleshooting and Debugging Questions

Covers structured methods for diagnosing and resolving software defects and technical problems at the code and system level. Candidates should demonstrate methodical debugging practices such as reading and reasoning about code, tracing execution paths, reproducing issues, collecting and interpreting logs metrics and error messages, forming and testing hypotheses, and iterating toward root cause. Topic includes use of diagnostic tools and commands, isolation strategies, instrumentation and logging best practices, regression testing and validation, trade offs between quick fixes and long term robust solutions, rollback and safe testing approaches, and clear documentation of investigative steps and outcomes.

MediumTechnical

31 practiced

A recent configuration change caused a spike in 502 errors. Design a safe rollback plan that minimizes customer impact: include immediate steps to rollback, verification checks to confirm success, strategies for partial rollbacks/canaries, and communication points with stakeholders. Also list safeguards to avoid repeating the same mistake on the next deployment.

EasyTechnical

31 practiced

A background job on a single server fails intermittently once per day under heavy load; the bug doesn't reproduce in staging. Describe a reproducibility strategy you would use to capture the failure reliably. Include: how you would reduce the search space, what logging/metrics/traces you'd enable, use of snapshots or VM cloning, and how to safely increase load to reproduce without impacting production availability.

HardSystem Design

27 practiced

Design an observability platform for a mid-size company with 1,000 hosts, services generating ~1 TB of logs/day, metrics at 100k samples/sec, and a retention requirement of 30 days for logs and 365 days for aggregated metrics. Describe architecture components (agents/collectors, storage, index/search, tracing, alerting), sampling and retention strategies, cost controls, and how runbooks/alerting would be organized for operators.

HardSystem Design

39 practiced

Design an automated regression-test harness for Ansible playbooks that must manage ~2,000 servers. Include strategies to test idempotence, detect drift, validate critical changes (reboots, kernel updates), runbook integration, and how to stage tests to minimize risks and CI cost. Describe the CI pipeline and how to gate changes safely.

HardTechnical

27 practiced

Design a canary deployment strategy for a service serving 100k RPS across 1,000 hosts. Define the automated rollout plan, canary sizing and ramping schedule, metrics and statistical tests to decide success/failure, and automated rollback criteria. Include how to minimize false positives and detect regressions quickly.

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