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Edge Case Handling and Debugging Questions

Covers the systematic identification, analysis, and mitigation of edge cases and failures across code and user flows. Topics include methodically enumerating boundary conditions and unusual inputs such as empty inputs, single elements, large inputs, duplicates, negative numbers, integer overflow, circular structures, and null values; writing defensive code with input validation, null checks, and guard clauses; designing and handling error states including network timeouts, permission denials, and form validation failures; creating clear actionable error messages and informative empty states for users; methodical debugging techniques to trace logic errors, reproduce failing cases, and fix root causes; and testing strategies to validate robustness before submission. Also includes communicating edge case reasoning to interviewers and demonstrating a structured troubleshooting process.

MediumTechnical
0 practiced
Explain how you'd use dbt to add automated tests that catch edge cases for a metric 'net_revenue' including NULLs, negative refunds, integer overflow, and late-arriving refunds. Provide examples of dbt schema tests and a custom SQL test you might write.
HardTechnical
0 practiced
Create a comprehensive set of test cases and expected outputs for an ETL job that converts multi-currency amounts to USD, handles negative refunds, and rounds to 2 decimals. Include edge cases: unknown currency codes, extreme exchange rates, zero and NULL values, negative zero, and precision loss.
HardTechnical
0 practiced
You and a product manager disagree: they claim a particular unusual input is expected behavior while you believe it is an edge case that requires defensive handling. Describe your approach to resolve the disagreement, influence decision-making, and ensure appropriate tests are added without blocking deliverables.
HardTechnical
0 practiced
Weekly spikes in active users are flagged by your anomaly system. A deeper look shows out-of-order events from mobile SDKs are causing the spikes. Explain a plan to reproduce the issue, add guards to event processing to handle out-of-order events, reprocess affected windows, and ensure retention and cohort calculations remain correct after reprocessing.
EasyTechnical
0 practiced
You're building a Power BI report that groups sales by region. Sometimes the region field is NULL and the visual shows a blank slice, which confuses stakeholders. Describe the dataset-level and visualization-level options to handle NULL or unknown region values. For each option, state pros, cons, and impact on filtering and totals.

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