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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.

EasyTechnical
33 practiced
Describe the purpose of liveness and readiness checks for ETL jobs and connectors (for example: Kafka connectors, JDBC readers). Provide examples of checks (credential validity, ability to reach required services, thread health) and what orchestration systems should do on liveness/readiness failures.
EasyTechnical
42 practiced
A data pipeline intermittently fails with network timeouts when fetching from an upstream API. Describe a step-by-step debugging approach: reproduce locally or in staging, capture detailed logs and metrics (latencies, error codes), enable tracing/correlation IDs, implement retry/backoff and circuit breakers, and propose temporary mitigations and long-term fixes.
MediumTechnical
47 practiced
Implement a retry strategy for database writes used by your ETL job. Provide pseudocode that demonstrates exponential backoff with jitter, a max retry limit, and integration with idempotent upsert logic (e.g., using a unique key or upsert statement). Discuss when to abort and how to surface failures.
HardSystem Design
47 practiced
You're integrating with external enrichment APIs. Propose a design to implement circuit-breaker and bulkhead patterns in your ETL connectors: per-API circuit breakers, per-worker bulkheads, timeouts, retry budgets, and fallback behavior. Explain how to test these with fault injection and what metrics and alerts to monitor.
MediumTechnical
41 practiced
Design monitoring and alerting for data completeness and timeliness SLAs. What metrics would you track (row-count deltas, last-ingest timestamp, watermark lag), what alert thresholds and runbook actions would you define, and how would you show SLA health to business stakeholders?

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