Complex System Troubleshooting and Incident Diagnosis Questions

Tests systems thinking and approaches for diagnosing problems that span multiple components services layers or domains and present multiple related symptoms. Candidates should show how they map interdependencies prioritize which symptoms to address first generate and test hypotheses correlate telemetry across logs metrics and traces and distinguish root causes from secondary effects. The topic includes using instrumentation and monitoring to isolate failures reproducing issues in controlled environments understanding cascading failures and failure modes across networking storage database and application layers and applying mitigations rollbacks or fixes while minimizing user impact. Candidates should also describe incident communication documentation and post incident analysis to prevent recurrence.

MediumTechnical

0 practiced

During a major outage you are acting incident commander coordinating multiple teams. Describe how you structure the incident bridge (roles and responsibilities such as commander, scribe, communications, triage leads), decision points for mitigation versus rollback, and how to keep the bridge productive without micromanaging technical leads.

MediumTechnical

0 practiced

A bug causes intermittent request corruption only under high concurrency in production and you cannot reproduce it locally. Describe a methodical approach to recreate the issue in a controlled environment: which load simulation tools to use, checks for configuration and environment parity, ways to mirror production traffic, and how to instrument your test to capture the failing trace.

MediumTechnical

0 practiced

Frontend reports intermittent 5-10 second request latencies. Traces point to occasional long-running PostgreSQL queries. Describe how you would triage: identify problematic queries, detect lock or contention issues, diagnose IO stalls, and find indexing problems. Include the SQL commands and Postgres views you would use and low-risk mitigation steps you can apply without downtime.

HardSystem Design

0 practiced

Your service operates in two active regions behind a global load balancer. One region begins degrading (high latency and 50% errors) due to networking issues within that region. Explain, step-by-step, how you'd perform a safe failover to the healthy region while minimizing user impact and data loss. Cover DNS or anycast strategies, failover criteria, session affinity, database replication consistency, and rollback plans.

EasyTechnical

0 practiced

Define a cascading failure in a distributed system and give a concrete example (service A fails, retries overwhelm service B, etc.). Explain at least two design patterns you would implement to prevent small failures from escalating into system-wide outages and why they help.

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