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.

HardTechnical

0 practiced

A financial dashboard failed for an auditor due to a permission denial after a user synchronization job. Describe an incident-response style troubleshooting: immediate mitigations to restore access, forensic steps to find root cause across SSO/group sync/provisioning, tests to validate the fix, and long-term safeguards to avoid recurrence.

MediumTechnical

0 practiced

Provide three concrete examples of informative empty states for dashboards where a KPI returns no data (e.g., conversion rate undefined, no transactions in period). For each example include: suggested messaging, visual cues or placeholders, troubleshooting steps for users, and backend metrics to collect to detect the empty state.

EasyTechnical

0 practiced

Given a table transactions(transaction_id, user_id, amount, occurred_at) write an ANSI SQL query to compute average transaction amount per user over the past 90 days. Requirements: exclude NULL amounts, treat users with no transactions as NULL average, and avoid division-by-zero errors. Explain how your query defends against empty windows and suspicious values like negative amounts.

HardTechnical

0 practiced

Design a process and set of SQL tests to detect and reconcile outliers where a metric's value is orders of magnitude larger than historical maxima (possible integer overflow or mis-aggregation). Include how to create synthetic regression tests and how to safely rollback or backfill affected aggregates.

MediumTechnical

0 practiced

A query that normally runs in 2 seconds now takes 2 minutes and times out for some users. Walk through your debugging checklist: what SQL-level diagnostics and system-level checks would you run, and what short-term mitigations would you apply to restore access while you investigate?

Unlock Full Question Bank

Get access to hundreds of Edge Case Handling and Debugging interview questions and detailed answers.

Join thousands of developers preparing for their dream job.