DevOps Engineer Interview Questions
372 questions across 38 categories
The bulk of a working DevOps engineer's day-to-day: hands-on tooling, common troubleshooting, and the practical judgment calls that come up once you're actually operating systems.
When would you actually prefer blue-green deployment over canary, even for a system where reliability is critical?
IntermediateCI/CD6 min
When does autoscaling actually save money compared to a well-chosen fixed capacity, and when can it end up costing more?
IntermediateAWSKubernetes6 min
How would you decide what mix of Reserved Instances, Spot Instances, and On-Demand capacity to use across a workload with both steady baseline traffic and unpredictable spikes?
IntermediateAWS7 min
An audit finds most of your EC2 instances are running at under 15% average CPU utilization. How would you approach rightsizing them without risking a performance incident?
IntermediateAWS6 min
This month's cloud bill came in 3x higher than usual, with no corresponding increase in traffic or deliberate infrastructure change. How do you actually track down the cause?
IntermediateAWS8 min
What's the actual difference between RPO and RTO, and how does each change depending on whether you're designing for multi-AZ or multi-region failover?
IntermediateAWS6 min
A junior engineer asks why deploying across multiple Availability Zones in the same region isn't enough for 'true' disaster recovery. How would you explain the actual distinction between AZs and regions?
BeginnerAWS6 min
Finance is asking why the same infrastructure spend that used to be a predictable annual budget line is now a variable monthly cloud bill that's harder to forecast. How would you explain this shift?
BeginnerCloud Fundamentals5 min
A system that can scale from 10 to 1,000 servers is described as both 'scalable' and 'elastic' — are these actually the same property, and does the distinction matter practically?
BeginnerCloud Fundamentals5 min
What's the actual difference between IaaS, PaaS, and SaaS, and how would you decide which one is the right fit for a given workload?
BeginnerCloud6 min
How would you evaluate whether to move an existing IaaS-hosted application to a PaaS, given the migration cost involved?
IntermediateCloud7 min
A customer asks how their data stays isolated from other customers on the same physical cloud infrastructure. What's actually happening under the hood to make multi-tenancy safe?
IntermediateCloud Fundamentals6 min
What operational risks does heavy reliance on SaaS introduce that IaaS or PaaS generally don't — vendor lock-in and data portability included?
IntermediateCloud6 min
Where does serverless (e.g. AWS Lambda) actually fit on the IaaS/PaaS/SaaS spectrum — does it fit cleanly into any of those three categories at all?
IntermediateAWS6 min
A company got breached because an S3 bucket was publicly accessible, and leadership initially blamed AWS. Why is that framing wrong, and how does the shared responsibility model actually draw the line?
BeginnerAWS6 min
Leadership is nervous about 'vendor lock-in' and wants every architectural decision evaluated for portability across cloud providers. Is this concern well-founded, or often overstated?
IntermediateCloud Fundamentals6 min
What's actually the difference between a container and a virtual machine, at the operating system level — not the marketing-slide version?
BeginnerContainersLinux7 min
How would you explain the security trade-off between containers and VMs to someone deciding whether to run untrusted third-party code?
IntermediateContainers6 min
Why does a container image being much smaller than a VM image matter for both startup time and attack surface, specifically?
BeginnerDockerContainers6 min
What specific Linux namespace types exist, and what does each one actually isolate for a containerized process?
IntermediateLinuxContainers7 min
Kubernetes dropped direct Docker support years ago in favor of containerd/CRI-O. What's the actual relationship between Docker, containerd, and CRI-O, and why did this change happen?
IntermediateContainersKubernetes7 min
What does it actually mean for a container image to be 'OCI-compliant,' and why does that matter beyond just being a compatibility buzzword?
IntermediateContainers6 min
How does a container image's layered filesystem actually work at the OS level — what makes writes inside a running container not modify the underlying image?
IntermediateContainersLinux6 min
Your database backups have been running successfully every night for two years, but nobody has ever actually restored one. Why is that a real risk, and how would you fix it?
IntermediateDatabases6 min