Covers the ability to diagnose, triage, and resolve complex technical problems end to end while demonstrating personal ownership. Candidates should show deep technical reasoning about system architecture, integration complexity, data migration considerations, and custom configuration trade offs. Expect discussion of root cause analysis, diagnostic techniques, reproducible debugging, and risk mitigation strategies. Candidates should be able to explain design trade offs, propose practical solutions, assess business impact, and describe collaboration with stakeholders and cross functional teams. Emphasis should be placed on concrete actions the candidate took, how they prioritized options, and the measurable results and lessons learned.
HardTechnical
22 practiced
Theoretical (hard): Describe an end-to-end testing strategy to catch high-severity incidents before they reach production. Discuss contract tests, integration tests, canary deployments, synthetic monitoring, chaos engineering, and the trade-off between test coverage, speed, and maintenance cost. Provide examples of what to test for a payment processing service.
HardTechnical
29 practiced
Program design (hard): Design an incident-readiness program for an engineering organization that reduces MTTR and improves cross-team coordination. Include training (on-call drills), runbook ownership, incident simulations (game days), measurable KPIs, tooling, and incentives to maintain readiness. Provide a rollout plan and ways to measure program effectiveness over a 12-month period.
MediumTechnical
30 practiced
Your service's P99 latency doubled over the last 24 hours but average CPU and throughput are unchanged and you have sparse tracing. Explain a practical investigation plan to identify root cause: which additional instrumentation would you add, how you'd collect micro-profiling data, how to use sampling vs full traces, and how to prioritize fixes when the root cause is multi-factor (e.g., GC, slow DB queries, and queue backpressure).
HardTechnical
29 practiced
Coding (Java, hard): Given a list of Alert objects {timestamp: long (ms), fingerprint: String}, implement a function that merges alerts into incidents when consecutive alerts with the same fingerprint occur within 5 minutes of each other. Return a list of Incident objects {fingerprint, startTimestamp, endTimestamp, count}. Assume alerts may be unsorted; aim for O(n log n) time. Provide Java code or a close pseudocode implementation.
HardTechnical
25 practiced
Theoretical/Design (hard): How would you design SLOs and SLIs for critical downstream dependencies (e.g., third-party payment gateway, auth provider) that your service relies on? Describe how breaches in those SLOs should affect your own service's behavior (circuit-break, degrade, fallbacks), contractual SLA considerations, and how to surface dependency health to customers.
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