Troubleshooting interview prep

• Alert Fatigue and On-Call Burnout — Identify, measure, and systematically reduce alert noise to restore effective on-call rotations.
• Alerts Not Firing — Alert silence, inhibition, scrape failures, rule misconfiguration, dead man's switch, and alertmanager routing
• Canary Deployment Problems — Fix canary traffic routing, statistical validity, and monitoring gaps that make canaries unreliable.
• Connection Pool Exhausted — Connection pool sizing, max_connections, PgBouncer, RDS Proxy, idle connections, and leak detection.
• CoreDNS Failures in Kubernetes — Diagnose and fix CoreDNS failures that cause cascading service-to-service connectivity failures in Kubernetes.
• CPU Runaway Process Investigation — Identify and fix runaway CPU consumers using profiling tools across Python, JVM, Go, and Node.js.
• CrashLoopBackOff — Pod restart loop diagnosis, previous logs, init containers, liveness probes, resource limits, and config error
• Database Deadlock Diagnosis — Detect, interpret, and eliminate database deadlocks in PostgreSQL and MySQL production systems.
• Database Migrations in Production — Execute zero-downtime database schema changes safely in production PostgreSQL and MySQL systems.
• Deployment Rollback Strategies — Design rollback-capable deployment pipelines and untangle database migrations from code deployments.
• Disk IOPS Saturation — Diagnose and resolve disk IOPS bottlenecks on EBS volumes and database instances under load.
• DNS Failures — NXDOMAIN vs SERVFAIL, TTL propagation, negative caching, Kubernetes CoreDNS failures, and split-horizon issues
• EC2 Instance Unresponsive — SSH unreachable, console output, system logs, kernel panic, disk full, and rescue mode.
• ECS Task Failures and Restarts — Identify why ECS tasks stop unexpectedly and prevent restart loops from impacting availability.
• ELB 5xx Errors — HTTP 502, 503, 504 from ALB — distinguishing LB errors from backend errors and diagnosing each.
• Flaky CI/CD Pipeline Failures — Systematically identify and eliminate flaky tests and infrastructure failures that erode CI trust.
• HPA Not Scaling — HPA metrics server, custom metrics, stabilization window, scale-down cooldown, and resource request prerequisi
• IAM Permission Denied Errors — Trace IAM AccessDenied errors through policy layers to find the blocking rule.
• JVM Garbage Collection Pauses — Diagnose and reduce JVM GC pause times that cause latency spikes and health check failures.
• Kubernetes Service Not Reachable — Systematically debug Kubernetes Service connectivity failures using endpoints, selectors, and DNS.
• Lambda Cold Start Latency — Diagnose and eliminate Lambda initialization latency that spikes p99 response times.
• Log Volume Explosion and Cost Runaway — Identify and eliminate runaway log volume that drives unexpected observability cost spikes.
• Memory Leak Diagnosis — Container OOMKill events, heap dumps, JVM tuning, Go pprof, Python tracemalloc, and RSS growth patterns.
• Metrics Gaps in Dashboards — Diagnose and resolve missing data points in Prometheus, CloudWatch, and Grafana dashboards.
• Missing Traces in Distributed Tracing — Diagnose why traces are incomplete or missing in Jaeger, Zipkin, or OpenTelemetry-based systems.
• Multi-Region High Latency — Optimize cross-region latency using AWS backbone routing and data gravity principles.
• NAT Gateway Bandwidth and Throttling — Identify NAT Gateway connection limits and eliminate unnecessary NAT costs with VPC endpoints.
• Network Bandwidth Saturation — Detect and resolve network bandwidth saturation on EC2 instances and container workloads.
• OOMKilled Pod Diagnosis — Diagnose OOMKilled container failures in Kubernetes using metrics, heap dumps, and memory profiling.
• Packet Loss and Network Degradation — Distinguish packet loss from latency using retransmission metrics and MTU diagnostics.
• Pods Stuck Pending — Scheduler events, insufficient resources, taints/tolerations, affinity rules, and PVC binding failures.
• PVC Mount Failures in Kubernetes — Resolve PersistentVolumeClaim mount failures including Multi-Attach errors and CSI provisioning issues.
• RDS CPU at 100% — Performance Insights, slow query log, EXPLAIN, missing indexes, autovacuum, and connection storms.
• RDS Read Replica Replication Lag — Diagnose and reduce replication lag on RDS read replicas to ensure data freshness for reads.
• S3 High Latency Spikes — Diagnose S3 request latency spikes and design prefix strategies to avoid throughput limits.
• Slow Query Diagnosis — pg_stat_statements, slow query log, EXPLAIN ANALYZE, missing indexes, N+1 queries, and query rewrites.
• Staging Passes, Prod Fails — Environment parity, config differences, data volume, external dependencies, feature flags, and infrastructure
• TLS Certificate Expiry Incidents — Detect expiring certificates before they cause outages and automate renewal pipelines.
• VPC Connectivity Failures — Security groups, NACLs, routing, VPC peering, NAT gateway failures, and VPC Flow Logs diagnosis.
• Zero-Downtime Schema Changes — Expand-contract pattern, online schema changes, column renames, index creation, and backward compatibility.

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