Debugging and Recovery Under Pressure Questions

Covers systematic approaches to finding and fixing bugs during time pressured situations such as interviews, plus techniques for verifying correctness and recovering gracefully when an initial approach fails. Topics include reproducing the failure, isolating the minimal failing case, stepping through logic mentally or with print statements, and using binary search or divide and conquer to narrow the fault. Emphasize careful assumption checking, invariant validation, and common error classes such as off by one, null or boundary conditions, integer overflow, and index errors. Verification practices include creating and running representative test cases: normal inputs, edge cases, empty and single element inputs, duplicates, boundary values, large inputs, and randomized or stress tests when feasible. Time management and recovery strategies are covered: prioritize the smallest fix that restores correctness, preserve working state, revert to a simpler correct solution if necessary, communicate reasoning aloud, avoid blind or random edits, and demonstrate calm, structured troubleshooting rather than panic. The goal is to show rigorous debugging methodology, build trust in the final solution through targeted verification, and display resilience and recovery strategy under interview pressure.

HardTechnical

0 practiced

Design a debugging playbook to triage and fix bad data introduced by a recent change, covering immediate mitigation, minimally invasive fix, verification, backfill plan, and postmortem. The playbook must be executable by an on-call engineer with 30 minutes of context. Provide a short checklist and example commands (SQL or CLI) for key steps.

EasyTechnical

0 practiced

You are given this Python function used in an ETL transform. It should return the median of a list of integers but fails on even-length inputs.

python

def median(nums):
    nums = sorted(nums)
    n = len(nums)
    return nums[n//2]

Explain the bug, provide the corrected implementation in Python, and describe test cases you'd run to validate the fix.

HardTechnical

0 practiced

A production consumer throws 'ClassNotFoundException' reading serialized objects produced by your job. Provide a prioritized debugging checklist to trace serialization mismatches (Kryo, Java serialization, Avro), what artifacts to collect from both producer and consumer, and a hotfix plan compatible across versions without full redeploy.

EasyTechnical

0 practiced

You're asked to write a short testing checklist for a new ETL transform. The checklist must include representative test cases: normal, edge (empty and single-row), duplicates, boundary values, large inputs, and randomized stress tests. Provide a concise checklist and explain why each case matters and how you'd automate the checks.

EasyTechnical

0 practiced

Explain how you would use git bisect (binary search across commits) to find a commit that introduced a regression in a data pipeline test suite which fails intermittently in CI. Describe how to make the bisection reliable when tests are flaky and how to minimize developer time during the bisect.

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