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.

HardTechnical

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Hard: You're debugging a cross-service transaction that intermittently violates a business invariant (e.g., negative balance). Explain how you'd instrument end-to-end tracing, add assertion checks, and implement invariant-monitoring to detect and prevent propagation of corrupt data. Describe repair strategies for already-corrupted data.

MediumTechnical

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Medium: You are diagnosing a memory leak in a long-running Node.js service. Describe a step-by-step approach including commands/tools (e.g., heap snapshot, Chrome DevTools, heapdump, process.memoryUsage), what to look for in snapshots, and how to validate a candidate fix in staging before rolling to production.

MediumTechnical

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Medium: Explain how static analysis and linters can help reduce the debugging surface. Give three concrete examples of bugs or classes of bugs that static tools catch and how you'd integrate these tools into a CI pipeline.

EasyTechnical

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Write a short Python helper that wraps a function and logs execution time and exceptions for diagnostic purposes. Signature: `def instrument(func):` should return a wrapper. The wrapper should log start/end timestamps and exception stack traces using the standard `logging` module. Provide the implementation and a brief explanation of why such an instrumentation wrapper is useful in debugging.

HardSystem Design

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Hard: Design an automated system to triage incoming bug reports by correlating logs, traces, and metrics to suggest the most likely root cause. Describe inputs, heuristics or ML approaches, how to weight signal from logs vs traces, privacy considerations, and how you'd measure the triage system's accuracy.

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