DevOps interview questions, answered properly
209 questions from real DevOps, SRE and platform interviews. Each page gives you the answer interviewers are listening for, why they ask it, and the follow-ups they use to find the edge of your knowledge.
Docker
- Alpine vs Distroless vs Scratch - Base Image Showdown
- BuildKit Secrets - Stop Baking Keys Into Images
- BuildKit vs Legacy Builder - 10x Faster Docker Builds
- Docker Bridge vs Host vs None - 3 Network Modes
- Docker Build Secrets - Don't Leak Credentials
- Docker BuildKit - Faster Builds with Parallel Stages
- Docker Compose - Multi-Container Apps Made Easy
- Docker Container Won't Start - 5 Debug Steps
- Docker Disk Full - Clean Up Images Volumes Layers
- Docker Healthcheck - Catch Dead Containers Early
- Docker Image Hardening - Security Checklist
- Docker Image Has 500 CVEs - Fix Your Base Image
- Docker Logs Missing - Fix Container Log Rotation
- Docker Networking - Bridge Host None Overlay
- Docker Networking Issues - Container Can't Reach Host
- Docker Run as Non-Root - Stop This Bad Practice
- Docker Secrets vs Env Vars - Stop Leaking Credentials
- Docker Socket Exposed - Why That's Dangerous
- Docker Volumes vs Bind Mounts - When to Use Each
- Docker vs Podman vs Containerd - Container Runtimes
- ENTRYPOINT vs CMD - The Difference That Bites
- Multi-Stage Builds - Cut Image Size 80%
- Multi-Stage Builds - Shrink and Secure Your Images
- Rootless Docker - Run Containers Without Root
- Why Your App Needs More Than One Container
Kubernetes
- ClusterIP vs NodePort vs LoadBalancer vs Ingress
- DaemonSets Explained - One Pod Per Node
- ImagePullBackOff - Debug Container Pull Failures
- Init Containers - Run Setup Before Your App Starts
- Jobs and CronJobs - Batch Processing in K8s
- K8s In-Place Pod Scaling - No Restart Required
- Karpenter vs Cluster Autoscaler - Node Scaling Compared
- KEDA - Event-Driven Autoscaling for Kubernetes
- Kubernetes DNS Not Resolving - Troubleshoot CoreDNS
- Kubernetes Events - The Debug Tool You're Ignoring
- Network Policies - Stop Lateral Movement in 3 Rules
- Node NotReady - Debug Kubernetes Node Failures
- Persistent Volumes Explained - PV PVC StorageClass
- Pod Priority and Preemption - Who Gets Evicted?
- RBAC in Kubernetes - Roles and ClusterRoles
- Secrets vs ConfigMaps vs External Secrets - When to Use
- Service Mesh Explained - Do You Actually Need Istio?
- Taints Tolerations and Node Affinity - Quick Guide
- VPA vs HPA - When to Use Which?
Linux
- Bash Scripting Tips for DevOps - 5 Must-Know Tricks
- Btrfs vs ZFS: Which Snapshot King Wins?
- ext4 vs XFS vs ZFS - Linux Filesystems Compared
- iptables vs nftables vs eBPF - Linux Firewalls
- Linux Audit Framework - Track Who Did What
- Linux File Permissions - chmod chown Explained
- Linux High CPU - Find the Rogue Process Fast
- Linux Network Troubleshooting - ss netstat traceroute
- Linux Server Hacked - 5 Forensics Steps
- perf top - Spot CPU Bottlenecks Fast
- SELinux vs AppArmor - Mandatory Access Control Compared
- SSH Hardening - 5 Steps Every Server Needs
- strace - Debug Syscalls Like a Senior Engineer
- systemd vs init - Why Linux Switched
- systemd vs init vs supervisord - Process Managers
- tcpdump in 60 Seconds - Capture Any Packet
- tcpdump vs Wireshark - Capture Network Traffic
Observability
- AI DevOps Copilot - Is It Actually Useful?
- Alert Fatigue - 4 Ways to Kill Noisy Alerts
- Correlation IDs: Tracing a Request Across Services
- Distributed Tracing with OpenTelemetry - Quick Start
- Grafana Dashboards - 5 Design Rules That Work
- Jaeger vs Zipkin vs Tempo - Tracing Tools Compared
- Loki vs Elasticsearch - Cheaper Log Storage
- OpenTelemetry Collector - Unified Telemetry Pipeline
- OpenTelemetry vs Datadog APM vs New Relic
- PagerDuty vs Opsgenie - On-Call Tool Comparison
- Prometheus PromQL - 5 Queries You Must Know
- RED vs USE Method - Which Metrics to Track
- SLO-Based Alerting - Stop Alert Fatigue for Good
- Structured Logging - Why and How
- Thanos vs Cortex vs Mimir - Long-Term Prometheus Storage
Networking
- BGP in 60 Seconds - How the Internet Routes
- Cilium vs kube-proxy - Why eBPF Wins
- Connection Refused vs Timeout - Different Fixes
- CORS Errors - Why Your API Calls Fail
- DNS for DevOps - A, CNAME + TTL in 60 Seconds
- DNS Resolution Failed - 5 Debug Steps
- Keepalive vs Timeout - Tune TCP for Production
- Kubernetes Ingress vs Gateway API - What Changed
- mTLS vs TLS vs IPSec - Encryption in Transit
- Packet Loss in Prod - 4 Steps to Find the Drop
- Reverse Proxy vs Load Balancer vs API Gateway
- Route 53 vs Cloudflare DNS vs Google Cloud DNS
- Service Mesh vs API Gateway - When to Use Which
- SSL Certificate Expired in Production - Quick Fix
- Why Your API Works in Postman But Breaks in the Browser
DevSecOps
- AWS Keys Leaked on GitHub - 5 Minute Fix
- Container Escape - 3 Ways Attackers Break Out
- Cosign vs Notation - Sign Container Images
- DAST in CI/CD - Runtime Security Testing
- Dependency Confusion Attack - How It Works and Prevention
- Distroless Images - Cut Container CVEs to Zero
- External Secrets Operator - Sync Vault to Kubernetes
- GitHub Dependabot vs Renovate - Auto-Patch Compared
- Kyverno vs OPA - Kubernetes Policy Engines Compared
- OPA Gatekeeper - Block Bad K8s Configs in 3 Rules
- Sigstore and Cosign - Sign Your Container Images
- Software Supply Chain Security - SBOM Explained
- Trivy vs Grype vs Snyk - Which Scanner Wins?
Compliance
- Audit Logging - Build a Compliance-Ready Pipeline
- AWS Config Rules - Enforce Compliance Automatically
- CIS Benchmarks - Harden Your Servers Automatically
- Cloud Audit Logs - Who Changed What and When
- GDPR and Cloud - Data Residency Requirements
- ISO 27001 for DevOps - 5 Controls You Need
- PCI DSS for DevOps - What Pipelines Must Do
- SBOM Explained - Software Bill of Materials in 30s
- Secrets Rotation - Automate or Get Breached
- Signed Container Images - Verify Before Deploy
- SOC2 for DevOps - What You Actually Need
- SOC2 Type I vs Type II - What's the Difference?
Terraform
- OpenTofu vs Terraform - Should You Switch?
- OpenTofu vs Terraform 2026 - Should You Switch Now?
- Terraform for_each vs count - Stop Using count
- Terraform Import - Bring Existing Resources Under Control
- Terraform Modules - Reusable Infrastructure
- Terraform Moved Blocks - Refactor Without Destroy
- Terraform State Backend - S3 vs Terraform Cloud
- Terraform vs OpenTofu - 2026 Migration Guide
- Terraform vs OpenTofu vs Pulumi - IaC Showdown 2026
- Terraform Workspaces - Multi-Environment Management
- Terragrunt - DRY Terraform at Scale
FinOps
- AWS Reserved Instances vs Savings Plans - Which to Choose?
- Cloud Cost Tagging Strategy That Actually Works
- FinOps in CI/CD - Cost Gates Before Deploy
- FinOps Maturity Model - Crawl Walk Run
- GCP Committed Use Discounts - How They Actually Work
- Karpenter vs Cluster Autoscaler - Cost Comparison
- Kubernetes Cost Optimization - Right-Size Your Pods
- S3 Storage Classes - Stop Overpaying for Storage
- Spot Instances for CI/CD - Save 90% on Build Costs
- What is FinOps? Cloud Cost Management Explained
Scenario-Based
- 5xx Errors After Deploy - Rollback Decision Tree
- Container OOMKilled - Why and How to Fix
- Deployment Broke SSL Certs - Quick Fix
- Design a Multi-Tenant SaaS Deployment Pipeline
- Disk Pressure Evicting Pods - Fix in 3 Steps
- Docker Build Cache Invalidated - Speed Up Builds
- Memory Leak in Prod - Debug in 5 Steps
- Pod CrashLoopBackOff - 5 Common Causes
- Zero-Downtime Kubernetes Upgrade Strategy
AWS
- AWS Control Tower: Auto-Enforce Account Guardrails
- AWS EventBridge - Event-Driven Architecture
- AWS IAM Best Practices - Least Privilege Done Right
- AWS Lambda Cold Starts - Causes and Fixes
- AWS Organization SCPs - Guardrails for Multi-Account
- AWS SSM vs SSH - Stop Opening Port 22
- AWS VPC Design - Subnets NAT and Security Groups
- ECS vs EKS vs Lambda - When to Use Which?
- S3 vs EFS vs EBS - Pick the Right Storage
CI/CD
- Canary Deployments - Test in Production Safely
- Feature Flags - Deploy Without Releasing
- GitHub Actions - Reusable Workflows Explained
- GitHub Actions Matrix Strategy - Test Across Versions
- GitHub Actions Self-Hosted Runners - Setup Guide
- Jenkins Shared Libraries - DRY Your Pipelines
- Jenkins vs GitHub Actions vs GitLab CI - 2026 Comparison
- Trunk-Based Development - Why It Beats GitFlow