Systematic Troubleshooting and Debugging Questions

Covers structured methods for diagnosing and resolving software defects and technical problems at the code and system level. Candidates should demonstrate methodical debugging practices such as reading and reasoning about code, tracing execution paths, reproducing issues, collecting and interpreting logs metrics and error messages, forming and testing hypotheses, and iterating toward root cause. Topic includes use of diagnostic tools and commands, isolation strategies, instrumentation and logging best practices, regression testing and validation, trade offs between quick fixes and long term robust solutions, rollback and safe testing approaches, and clear documentation of investigative steps and outcomes.

HardTechnical

29 practiced

Draft an outline for a high-quality postmortem template for complex network incidents that ensures clear root cause, timeline, contributing factors, corrective actions, validation tests, and owners. List artifacts to attach (pcaps, configs, alerts), how to calculate SLO impact, and how to use the postmortem to prevent recurrence.

EasyTechnical

59 practiced

You run traceroute from host A to host B and see the following output:\ntraceroute to 10.0.2.5, 30 hops max\n 1 10.0.1.1 1.0 ms 1.2 ms 1.1 ms\n 2 192.0.2.1 10.3 ms 10.2 ms 10.4 ms\n 3 203.0.113.10 * * *\n 4 203.0.113.20 120 ms 119 ms 118 ms\nExplain what the '*' at hop 3 indicates, whether hop 3 is necessarily the cause of the latency seen at hop 4, and list the next diagnostic commands you would run.

MediumTechnical

39 practiced

Traffic from a particular subnet is saturating an uplink at sporadic times. Explain how you'd use NetFlow/IPFIX or sFlow to identify top talkers, the application/port mix, and whether the traffic is ephemeral or sustained. Discuss sampling effects and how you'd validate flow conclusions with packet captures.

HardSystem Design

28 practiced

You face an intermittent failure that only appears under heavy cross-traffic when a specific AS path through a third-party provider is present. Design a reproducible test harness and instrumentation strategy to simulate the AS path conditions and cross-traffic, capture metrics, and isolate the root cause. Mention lab topology, traffic generators, BGP route manipulation, and validation metrics.

HardSystem Design

36 practiced

Design an observability plan and SLO/SLA monitoring strategy for a global network fabric that supports microservices. Include which metrics, logs, and traces to collect from routers, switches, firewalls, and load balancers; recommended sampling rates; retention policies; alert thresholds; dashboards; and how you'd correlate network events with application metrics for incident triage.

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