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DevOps Mock Interview: 20 Questions in 50 Minutes

Four rounds that copy a real interview. Answer aloud, then check the model answers.

Mock interview format

  1. Warm-up · 5 minutes — 4 questions
  2. Technical · 20 minutes — 7 questions
  3. Scenario · 15 minutes — 5 questions
  4. HR & behavioural · 10 minutes — 4 questions

Tip: record yourself and listen back. Most people talk too fast and skip the key idea.

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01

What is the difference between a container and a virtual machine?

Warm-upDocker and ContainersEasy
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A virtual machine runs a full guest operating system on a hypervisor, so it is heavier, takes minutes to boot and uses gigabytes. A container shares the host kernel and isolates only the application and its dependencies using namespaces and cgroups, so it starts in seconds and uses far less memory. VMs give stronger isolation; containers give density and portability.
02

What is a webhook and how does it trigger a build?

Warm-upCI/CD PipelinesEasy
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A webhook is an HTTP callback: when an event happens in the Git server, such as a push or pull request, it sends a POST request with event details to a configured URL. Jenkins or another CI tool receives it and starts the matching pipeline immediately. This is better than polling the repository every few minutes, which wastes resources and delays feedback.
03

What is .gitignore and how do you stop tracking a file that is already committed?

Warm-upGit and Version ControlEasy
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A .gitignore file lists patterns such as node_modules/, *.log or .env that Git should not track. It only affects untracked files, so a file already committed keeps being tracked. To stop tracking it, run git rm --cached <file>, add it to .gitignore and commit. If it held a secret, the old commits still contain it and the secret must be rotated.
04

What is the difference between continuous integration, continuous delivery and continuous deployment?

Warm-upCI/CD PipelinesEasy
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Continuous integration means developers merge small changes often and every merge is automatically built and tested. Continuous delivery goes further: every passing build is packaged and ready to release, but a human approves the production push. Continuous deployment removes that manual step, so every change that passes all checks goes to production automatically. Each stage needs more test confidence than the last.
05

How do you run a matrix build in GitHub Actions?

TechnicalCI/CD PipelinesMedium
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jobs: test: runs-on: ${{ matrix.os }} strategy: fail-fast: false matrix: os: [ubuntu-latest, windows-latest] python: ['3.11', '3.12'] steps: - uses: actions/checkout@v4 - uses: actions/setup-python@v5 with: python-version: ${{ matrix.python }} - run: pip install -r requirements.txt - run: pytest This creates four parallel jobs; fail-fast false lets all finish so you see every failure.
06

What is the difference between an Ingress and a Service?

TechnicalKubernetesMedium
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A Service exposes a set of pods at layer 4. An Ingress is a layer 7 HTTP routing resource that maps hostnames and paths to services, for example api.example.com to the api service and /admin to another. It needs an ingress controller such as NGINX or a cloud controller to work. One Ingress with one load balancer can serve many services, and it handles TLS termination.
07

What is the difference between declarative and imperative IaC, and between Terraform and Ansible?

TechnicalInfrastructure as Code (Terraform and Ansible)Medium
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Declarative tools describe the end state and the tool works out the steps; imperative tools describe the steps. Terraform is declarative, keeps a state file and is best at provisioning cloud resources. Ansible is procedural with mostly idempotent modules, agentless over SSH, and best at configuring servers and deploying software. Many teams use Terraform to create VMs and Ansible to configure them.
08

What are Terraform modules?

TechnicalInfrastructure as Code (Terraform and Ansible)Medium
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A module is a reusable folder of Terraform files with input variables and outputs, for example a vpc module or an eks-cluster module. The root module calls child modules with different values for each environment. Modules reduce duplication and enforce standards across teams. They can come from local paths, Git or the Terraform Registry and should be pinned to versions.
09

Explain liveness, readiness and startup probes.

TechnicalKubernetesMedium
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A liveness probe checks whether the container is healthy; if it fails, the kubelet restarts it. A readiness probe checks whether it can serve traffic; if it fails, the pod is removed from service endpoints but not restarted. A startup probe gives slow-starting apps time to boot and holds off the other probes until it succeeds. Wrong liveness probes can cause restart loops.
10

Write an IAM policy that gives read-only access to one S3 bucket.

TechnicalAWS Cloud for DevOpsMedium
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{ "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": ["s3:ListBucket"], "Resource": "arn:aws:s3:::acme-reports" }, { "Effect": "Allow", "Action": ["s3:GetObject"], "Resource": "arn:aws:s3:::acme-reports/*" } ] } ListBucket applies to the bucket ARN and GetObject to object ARNs, so both resources are needed.
11

What is an inode in Linux?

TechnicalLinux and Shell ScriptingMedium
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An inode is a data structure that stores a file's metadata: owner, permissions, size, timestamps, link count and pointers to data blocks, but not the file name. Names live in directory entries that map to inode numbers. A file system has a fixed number of inodes, so millions of tiny files can exhaust them while disk space is still free; check with df -i.
12

How do you handle secrets in Terraform and Ansible?

ScenarioInfrastructure as Code (Terraform and Ansible)Hard
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Do not hard-code secrets in .tf files or playbooks. In Terraform, read them from AWS Secrets Manager or Vault data sources, mark variables sensitive, and protect state because it may still hold values. In Ansible, encrypt secret variable files with ansible-vault and supply the vault password from CI secrets, or look up values from Vault at runtime. Rotate anything exposed in Git.
13

The application cannot connect to an RDS database. What do you check?

ScenarioAWS Cloud for DevOpsMedium
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Confirm the endpoint, port, username and password. Check that the RDS security group allows inbound traffic on the database port from the application's security group, and that both are in reachable subnets of the same VPC or peered networks. Test with nc -zv endpoint 5432 from the app host. Also check the instance status, max connections and SSL requirements.
14

The host disk is filling up because of Docker. How do you clean up and prevent it?

ScenarioDocker and ContainersMedium
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Check usage with docker system df. Remove stopped containers, dangling images and unused networks with docker system prune, and old build cache with docker builder prune; be careful with the volumes flag. Container logs are a common culprit, so configure log rotation with max-size and max-file in daemon.json. In CI agents, schedule regular pruning jobs.
15

df shows the disk is 100 percent full but du does not find large files. What is happening?

ScenarioLinux and Shell ScriptingHard
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Usually a large file was deleted while a process still holds it open, so the space is not released. Run lsof +L1 or lsof | grep deleted to find the process and file. Restarting or reloading that process frees the space; if you cannot restart, truncate the file through /proc/<pid>/fd/<n>. The fix is proper log rotation with copytruncate or a reopen signal.
16

A worker node shows NotReady. What do you do?

ScenarioKubernetesHard
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Run kubectl describe node to see conditions such as MemoryPressure, DiskPressure or a kubelet that stopped posting status. SSH in and check systemctl status kubelet, the container runtime, journalctl -u kubelet, disk space and network to the API server. Pods on the node are evicted after a timeout. Cordon and drain it, fix or replace the node, and in cloud setups let the node group recreate it.
17

How would you convince a team that manages servers by hand to adopt Infrastructure as Code?

HR & behaviouralInfrastructure as Code (Terraform and Ansible)Hard
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I would start with their pain, such as slow environment setup or outages from manual changes, rather than the tool. Then I would codify one small, visible piece, for example a new staging environment, and show it rebuilt in minutes with a reviewed pull request. I would pair with team members, write simple docs and expand gradually, measuring time saved and incidents avoided.
18

Tell me about a time you migrated an application to Kubernetes.

HR & behaviouralKubernetesHard
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Situation: our monolith and five services ran on hand-managed VMs with frequent config drift. Task: I led the move to a managed Kubernetes cluster. Action: I containerised each service, wrote Helm charts, added probes and resource limits, set up Argo CD, and migrated one low-risk service first with a rollback plan. Result: deployments went from weekly to daily and VM costs dropped about 30 percent.
19

How do you handle pressure when a release is blocked close to a deadline?

HR & behaviouralCI/CD PipelinesMedium
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Situation: a security scan blocked our release one day before a client demo. Task: ship without ignoring the risk. Action: I checked the finding, confirmed it was a real vulnerable library, upgraded it, ran the full test suite and kept the product manager updated every few hours. Result: we released on time, and I added weekly dependency scans to avoid last-minute surprises.
20

How do you make your commits and pull requests easy for teammates to review?

HR & behaviouralGit and Version ControlEasy
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I keep each pull request focused on one change and small enough to review in about fifteen minutes. Commits have clear messages saying what and why. The description explains the problem, the approach, how I tested it and any risk or rollback step. I run linters and tests locally first, and I reply to every review comment, even if just to say done.

Frequently asked questions

How do I use this mock interview?

Set a 50-minute timer, answer every question aloud (or ask a friend to read them), and open answers only after each round. Note every question where your answer missed the key idea.

How often should I take a mock?

Once a week while preparing and once two or three days before a real interview. The question order is fixed, so for fresh practice use the company and experience pages too.

More ways to practise

Company-wise DevOps questionsExperience-wise DevOps questionsRole-wise DevOps questionsCity-wise DevOps questionsMost asked DevOps questionsScenario-based questionsPractical / hands-on questionsHR & behavioural questionsOnline assessment questionsTechnical round questionsManagerial round questionsDevOps topic sheets