40 questions with answers for candidates with 1 year of experience — 15 easy, 23 medium, 2 hard.
What interviewers expect: 1 year experience
With one year of experience, interviewers expect you to have worked on real pipelines and servers. Questions cover writing Jenkinsfiles or GitHub Actions workflows, debugging failed builds, Docker image optimisation, basic Kubernetes objects and common AWS services. Be ready to describe the tickets you handled, what broke and how you fixed it.
This set is weighted towards CI/CD Pipelines (7), Monitoring, Logging and SRE (6), Kubernetes (6), AWS Cloud for DevOps (5).
Pipeline debugging Dockerfiles and Compose Kubernetes basics Core AWS services
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git stash saves your uncommitted changes and cleans the working directory, so you can switch branches for an urgent fix. git stash list shows saved entries, git stash pop reapplies the latest and removes it, and git stash apply keeps it. Use git stash -u to include untracked files. It is a short-term tool; for longer work, commit on a branch.
02
What are the four golden signals, and the RED and USE methods?
The four golden signals are latency, traffic, errors and saturation. RED, for request-driven services, tracks rate, errors and duration. USE, for resources such as CPU, disks and network, tracks utilisation, saturation and errors. RED tells you whether users are hurting; USE helps find which resource is the bottleneck. Together they give a solid starting set of dashboards and alerts.
03
What is the difference between declarative and scripted Jenkins pipelines?
Both are written in a Jenkinsfile using Groovy. Declarative pipelines use a fixed structure with pipeline, agent, stages, steps and post blocks, which is easy to read, validate and maintain. Scripted pipelines start with node and allow full Groovy logic, giving more flexibility but more room for messy code. Most teams use declarative and drop into a script block only when needed.
04
Write an EC2 user data script that installs and starts a web server on boot.
#!/bin/bash
set -e
dnf update -y
dnf install -y nginx
systemctl enable --now nginx
TOKEN=$(curl -s -X PUT http://169.254.169.254/latest/api/token \
-H 'X-aws-ec2-metadata-token-ttl-seconds: 60')
ID=$(curl -s -H "X-aws-ec2-metadata-token: $TOKEN" \
http://169.254.169.254/latest/meta-data/instance-id)
echo "<h1>Served by $ID</h1>" > /usr/share/nginx/html/index.html
User data runs once as root on first boot; logs are in /var/log/cloud-init-output.log. This uses IMDSv2.
Kubernetes is an open-source container orchestration platform. You declare the desired state, such as five replicas of an API, and it schedules containers across nodes, restarts failed ones, scales them, balances traffic and rolls out updates. Companies use it to run many microservices reliably on shared infrastructure, on any cloud or on-premises, through managed services like EKS, AKS and GKE.
systemctl status nginx
sudo systemctl start nginx
sudo systemctl restart nginx
sudo systemctl enable nginx # start at boot
sudo systemctl disable nginx
journalctl -u nginx -f # follow service logs
sudo systemctl daemon-reload # after editing a unit file
Unit files live in /etc/systemd/system. enable creates the symlink for the boot target, while start only runs it now.
07
How do Docker image layers and build caching work?
Each Dockerfile instruction like RUN, COPY or ADD creates a layer. Docker caches layers and reuses them if the instruction and its inputs have not changed; once one layer changes, all later layers rebuild. So copy dependency files and install dependencies first, then copy source code. That way code changes do not reinstall all packages, and builds become much faster.
08
Tell me about a blameless post-mortem you were part of.
Situation: a certificate expired and our API was down for 40 minutes. Task: I wrote the post-mortem. Action: I built a timeline from logs and chat, and we focused on why the system allowed it rather than who forgot: renewal was manual and nothing alerted. Result: we automated renewal with cert-manager, added expiry alerts 21 days ahead, and tracked actions to closure.
09
How do you configure an S3 remote backend with locking?
terraform {
backend "s3" {
bucket = "acme-terraform-state"
key = "prod/network/terraform.tfstate"
region = "ap-south-1"
encrypt = true
use_lockfile = true
}
}
Then run terraform init (add -migrate-state if moving local state). Enable versioning on the bucket. Older setups use dynamodb_table = "tf-locks" instead of use_lockfile for locking.
Never store secrets in code or the Jenkinsfile. Use the CI tool's encrypted credentials store, such as Jenkins credentials or GitHub Actions secrets, or fetch them at runtime from HashiCorp Vault or AWS Secrets Manager. Prefer short-lived credentials, for example OIDC federation from GitHub Actions to AWS instead of long-lived keys. Mask secrets in logs and give each pipeline only the permissions it needs.
11
Explain Linux file permissions and what chmod 755 means.
Every file has read (4), write (2) and execute (1) bits for three classes: owner, group and others. chmod 755 gives the owner 7 (read, write, execute) and gives group and others 5 (read, execute). It is typical for scripts and directories that everyone may run or enter but only the owner may change. Use ls -l to see permissions.
12
Write a script that alerts when any disk partition is above 80 percent used.
#!/bin/bash
THRESHOLD=80
df -hP | awk 'NR>1 {gsub("%","",$5); print $5, $6}' | while read -r used mount; do
if [ "$used" -ge "$THRESHOLD" ]; then
echo "WARNING: $mount is ${used}% full on $(hostname)"
fi
done
df -P keeps each entry on one line, awk strips the percent sign, and the loop compares each value with the threshold.
A common pipeline is checkout, build or compile, unit tests, static analysis and security scans, packaging into an artefact or container image, pushing to a registry, deploying to a test or staging environment, running integration or smoke tests, an approval gate, and production deployment with monitoring. Fast checks run first so developers get feedback within minutes and slow tests run later.
14
You get an alert that the company website is down. What are your first steps?
Acknowledge the alert so others know you are on it. Check whether it is really down from outside with curl or an uptime checker, and whether it is all users or one region. Look at recent deployments or changes, then load balancer health, application logs and the database. If a recent change caused it, roll back first. Inform the team and escalate if you cannot fix it quickly.
15
Write PromQL queries for request rate, error rate and p95 latency.
# requests per second per service over 5 minutes
sum by (service) (rate(http_requests_total[5m]))
# error ratio (5xx)
sum(rate(http_requests_total{status=~"5.."}[5m]))
/ sum(rate(http_requests_total[5m]))
# p95 latency from a histogram
histogram_quantile(0.95,
sum by (le) (rate(http_request_duration_seconds_bucket[5m])))
rate() works on counters and handles resets; the le label holds histogram bucket bounds.
docker run -d --name api \
--memory=512m --memory-swap=512m \
--cpus=1.5 \
--restart=unless-stopped \
myapp:1.0
# change limits on a running container
docker update --memory=1g --memory-swap=1g api
If the process exceeds the memory limit it is OOM killed, so set application heap sizes below the limit. --cpus caps CPU time rather than reserving cores.
17
What is the difference between a security group and a network ACL?
A security group acts as a firewall for instances or network interfaces. It is stateful, so return traffic is allowed automatically, and it supports only allow rules. A network ACL works at the subnet level, is stateless, so inbound and outbound rules must both allow traffic, supports allow and deny rules, and evaluates rules in number order. Security groups are the main control.
18
A pod is in CrashLoopBackOff. How do you troubleshoot it?
The container starts and keeps crashing, and Kubernetes waits longer between restarts. Run kubectl describe pod to see events and exit codes, and kubectl logs <pod> --previous for the crashed container's output. Common causes are missing environment variables or secrets, bad config, failing database connections, a wrong command, an aggressive liveness probe, or exit code 137 meaning OOM kill.
19
Write a Prometheus alerting rule for a high error rate.
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.
22
A production deployment failed halfway. What do you do?
Assess impact quickly using monitoring and error rates. If users are affected, roll back to the last good version, which should be a single pipeline action redeploying the previous artefact. Communicate status to stakeholders. Then check pipeline logs and application logs to find the cause, fix it in a branch and redeploy. Afterwards, hold a blameless review and add a check to catch it earlier.
FROM nginx:1.27-alpine
COPY site/ /usr/share/nginx/html/
HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
CMD wget -qO- http://localhost/ || exit 1
# check status
docker inspect --format '{{.State.Health.Status}}' web
Docker marks the container healthy or unhealthy. Compose can wait on it with condition: service_healthy. Kubernetes ignores HEALTHCHECK and uses its own probes.
The kubelet cannot pull the image. Check the image name and tag for typos and confirm the tag exists in the registry. For private registries, verify an imagePullSecret is set and has valid credentials, or that node IAM roles allow pulling from ECR. Also check network access from nodes to the registry and registry rate limits. kubectl describe pod shows the exact error.
25
How do you create a new branch, push it and set the upstream?
git switch -c feature/payment-retry
# make changes
git add .
git commit -m "Add retry for failed payments"
git push -u origin feature/payment-retry
After -u (set upstream), plain git push and git pull work on this branch without naming the remote. Then open a pull request against main.
26
What is the difference between git revert and git reset?
git revert creates a new commit that undoes the changes of an earlier commit, leaving history intact, so it is safe on shared branches like main. git reset moves the branch pointer backwards and removes commits from the branch history, which is fine locally but forces others to deal with rewritten history if already pushed. Use revert for anything already public.
27
An Ansible playbook run against 100 servers failed on 7 of them. What do you do?
Check the output and the retry file or failed host list to see the error on those hosts, for example unreachable SSH, a missing package repo or full disk. Fix the cause, then rerun only those hosts with --limit. Because tasks are idempotent, rerunning on successful hosts is also safe. For rolling changes, use serial and max_fail_percentage to stop early on failures.
28
What is the Terraform state file and why is it important?
terraform.tfstate maps the resources in your code to real resources in the cloud, storing their IDs and attributes. Terraform compares code, state and reality to decide what to create, change or destroy. Without it Terraform would not know what it manages. It may contain secrets in plain text, so store it in a secure remote backend, never in Git.
29
What is the difference between a Pod, a ReplicaSet and a Deployment?
A Pod is the smallest deployable unit: one or more containers sharing network and storage. A ReplicaSet keeps a specified number of identical pods running. A Deployment manages ReplicaSets and adds rolling updates and rollbacks by creating a new ReplicaSet for each version. In practice you create Deployments and rarely touch ReplicaSets or bare pods directly.
30
How do you perform a rolling update and roll back a Deployment?
# update the image
kubectl set image deployment/api api=registry.example.com/api:1.5.0
kubectl rollout status deployment/api
# history and rollback
kubectl rollout history deployment/api
kubectl rollout undo deployment/api
kubectl rollout undo deployment/api --to-revision=3
# pause or restart
kubectl rollout pause deployment/api
kubectl rollout restart deployment/api
In GitOps setups, you change the image tag in Git instead and let Argo CD apply it.
31
What is the difference between monitoring and observability?
Monitoring tracks known metrics and alerts when they cross thresholds, answering whether something is wrong. Observability is the ability to understand any internal state from outside data, answering why, even for problems you did not predict. It rests on three pillars: metrics for trends, logs for detailed events and traces for following one request across services. Good systems need both.
32
Your CI pipeline takes 40 minutes. How would you speed it up?
Measure first: find which stages take longest. Then cache dependencies and Docker layers, run independent stages and test suites in parallel, split tests across agents, and run only affected modules in a monorepo. Move slow end-to-end tests to a later stage or nightly run while keeping fast unit tests on every commit. Use bigger or autoscaled agents if they are the bottleneck.
An IAM user is an identity for a person or app with long-term credentials. Groups collect users so permissions are managed together. Policies are JSON documents that allow or deny actions on resources. Roles are identities with temporary credentials that are assumed by services, such as EC2 or Lambda, or by users from other accounts. Prefer roles over access keys wherever possible.
A VPC is your private network with a CIDR range like 10.0.0.0/16. It is split into subnets in each Availability Zone. Public subnets have a route to an Internet Gateway; private subnets reach the internet only through a NAT Gateway in a public subnet. Route tables control traffic, security groups and NACLs filter it, and VPC endpoints give private access to services like S3.
35
Explain the Kubernetes Service types ClusterIP, NodePort and LoadBalancer.
A Service gives pods a stable IP and DNS name and load balances across them using label selectors. ClusterIP, the default, is reachable only inside the cluster. NodePort also opens a port, 30000 to 32767, on every node. LoadBalancer additionally asks the cloud provider to create an external load balancer pointing to the service. Each type builds on the previous one.
I enjoy both writing code and understanding how systems run in production, and DevOps sits between the two. In my projects I set up a CI pipeline and Docker deployment and liked seeing a change go from commit to live in minutes. I want to keep learning cloud, Kubernetes and automation, and help teams release faster with fewer failures.
37
How do you run stages in parallel in a Jenkins declarative pipeline?
COPY copies local files and directories into the image and does nothing else. ADD can also download from a URL and automatically extracts local tar archives. Because that extra behaviour can be surprising, best practice is to use COPY by default and ADD only when you specifically want tar extraction. For downloads, use curl in a RUN step so you can verify checksums.
40
You deleted a local branch that had unmerged commits. How do you recover it?
Git keeps unreferenced commits for a while. Run git reflog to see recent HEAD positions and find the last commit of that branch, or check the hash printed when you deleted it. Then recreate the branch with git branch feature-x <hash>. Reflog is local only, so this works on the same machine, and entries expire after about 90 days by default.
Frequently asked questions
What is asked in DevOps interviews for 1 year of experience?
With one year of experience, interviewers expect you to have worked on real pipelines and servers. Questions cover writing Jenkinsfiles or GitHub Actions workflows, debugging failed builds, Docker image optimisation, basic Kubernetes objects and common AWS services. Be ready to describe the tickets you handled, what broke and how you fixed it.
How many questions should I practise before a DevOps interview?
Work through all 40 questions here, then the company-wise sets for the employers you are targeting. Quality matters more than count: be able to explain why each answer is right.
Which topics matter most for 1 year of experience?
Focus first on Pipeline debugging, Dockerfiles and Compose, Kubernetes basics, Core AWS services.