Start by outlining a systematic diagnostic process that moves from external to internal factors, covering network, DNS, disk, memory, CPU, application, dependencies, and deploy issues. Then discuss both immediate remediation and long-term architectural and operational improvements to prevent recurrence and improve resilience.
Pro tip: Emphasize the importance of observability and automation in both diagnosis and prevention; mention specific tools and metrics you'd monitor, and how you'd use them to quickly identify the root cause.
Confirm the down page is real and determine if it's isolated to one server or widespread. Check monitoring dashboards, logs, and try accessing from different networks.
Rule out network issues (e.g., load balancer, firewall, routing), DNS resolution, and upstream dependencies (e.g., database, third-party APIs). Use tools like dig, traceroute, curl, and check dependency health.
Check CPU, memory, disk I/O, and disk space using top, free, df, iostat, etc. Look for resource exhaustion or bottlenecks that could cause the application to fail.
Review application logs, error messages, and stack traces. Check for recent code changes or configuration updates. Verify if the application process is running and listening on the correct port.
Suggest architectural changes like redundancy, auto-scaling, circuit breakers, and operational changes like better monitoring, alerting, canary deployments, and chaos engineering.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.