Curated interview practice questions with answers. These are practice scenarios, not a verified list of past interview questions.
About Cognizant hiring for DevOps roles
Cognizant is a US-headquartered IT services and consulting company with most of its workforce based in India. It provides application development, testing, cloud, digital engineering and data analytics services, with strong practices in healthcare, insurance and banking. In India it hires for programmer analyst, quality engineer and data roles through campus and off-campus programmes such as GenC.
For DevOps roles, this Cognizant practice set focuses most on Docker and Containers (5), Infrastructure as Code (Terraform and Ansible) (5), CI/CD Pipelines (5), Git and Version Control (5). It has 13 easy, 13 medium, 4 hard questions, so you can start easy and work up to the harder ones.
Company type
IT services
Headquarters
Teaneck, New Jersey, USA
Main India offices
Chennai, Bengaluru, Pune, Hyderabad, Kolkata
Cognizant DevOps interview process
Online assessment (aptitude + reasoning)
Coding assessment
Technical interview
HR round
Typical pattern based on public candidate experiences. Rounds vary by role, team and year.
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01
What is the difference between a Docker image and a container?
An image is a read-only template made of layers, containing the application, libraries and configuration, built from a Dockerfile. A container is a running instance of an image with a thin writable layer on top. You can start many containers from one image. Changes made inside a container are lost when it is removed unless they are stored in volumes.
The HPA periodically reads metrics from the metrics server or a custom metrics adapter and changes the replica count of a Deployment or StatefulSet to keep a target, for example 70 percent average CPU. It calculates desired replicas from current usage divided by the target, within min and max bounds, with stabilisation windows to avoid flapping. CPU-based HPA needs resource requests set.
terraform init downloads providers and modules and configures the backend. terraform fmt and validate check style and syntax. terraform plan shows what will be created, changed or destroyed without making changes. terraform apply executes the plan after confirmation. terraform destroy removes all managed resources. In CI, save the plan with -out and apply that exact plan after review.
04
You need one pipeline that deploys to dev, staging and production with approval before production. How do you design it?
Build and test once, publish a versioned artefact, then promote it through environments. Dev deploys automatically on merge, staging deploys after dev smoke tests, and production waits for a manual approval from authorised people using a Jenkins input step or GitHub environment protection rules. Keep environment-specific settings in config files or parameters, not separate pipelines, and record who approved each release.
05
What are Git hooks and how are they used in DevOps?
Hooks are scripts Git runs at events such as pre-commit, commit-msg and pre-push on the client, or pre-receive on the server. Teams use them to run linters, format code, block secrets or enforce commit message formats before code leaves a laptop. Client hooks are not shared by default, so tools like pre-commit or Husky manage them, and CI repeats the checks.
06
What is a multi-stage Docker build and why use it?
A multi-stage build uses several FROM instructions in one Dockerfile. Early stages contain compilers and build tools to produce the artefact; the final stage starts from a small runtime image and copies only the built output with COPY --from. The result is a much smaller image with fewer vulnerabilities, because build tools, source code and caches never reach production.
07
What are the S3 storage classes and lifecycle policies?
S3 Standard is for frequently accessed data. Standard-IA and One Zone-IA are cheaper for infrequent access but charge retrieval fees. Intelligent-Tiering moves objects automatically based on access. Glacier Instant, Flexible Retrieval and Deep Archive are for archives with slower, cheaper access. Lifecycle rules move objects between classes after a set age and delete old versions or logs automatically.
08
What is the difference between git fetch and git pull?
git fetch downloads new commits and branches from the remote into remote-tracking branches like origin/main without touching your working files. git pull is fetch followed by merge (or rebase if configured) into your current branch. Fetch is safer when you want to inspect incoming changes first with git log main..origin/main before integrating them.
Git is a distributed version control system that tracks changes to files; every clone has the full history and works offline. GitHub is a hosting service built around Git that adds remote repositories, pull requests, code review, issues and Actions for CI. Alternatives such as GitLab and Bitbucket offer similar features. You can use Git without GitHub, but not the other way round.
10
Write an Ansible playbook to install and start nginx.
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.
An SLI is a measured indicator, for example the share of requests served under 300 ms. An SLO is the internal target for it, such as 99.9 percent over 30 days. An SLA is the external contract with penalties, usually looser than the SLO. The error budget is the allowed unreliability, 0.1 percent here; while budget remains teams ship features, and when it runs out they focus on reliability.
13
Write a production-ready Dockerfile for a Node.js application.
FROM node:20-alpine
WORKDIR /app
ENV NODE_ENV=production
COPY package.json package-lock.json ./
RUN npm ci --omit=dev
COPY . .
USER node
EXPOSE 3000
CMD ["node", "server.js"]
Dependencies are copied and installed before source code so the layer is cached. npm ci gives reproducible installs, USER node avoids running as root, and exec form CMD lets the app receive signals.
14
What is an artefact repository and why is it used?
An artefact repository such as Nexus, JFrog Artifactory or a container registry stores versioned build outputs like JAR files, npm packages and Docker images. The pipeline builds once and promotes the same artefact through dev, staging and production, so what you tested is exactly what you deploy. It also caches public dependencies, speeds up builds and keeps release history for rollbacks.
15
When do you use a StatefulSet instead of a Deployment?
Use a StatefulSet for stateful workloads such as databases, Kafka or Elasticsearch that need stable identity. Pods get fixed names like db-0 and db-1, start and stop in order, and each gets its own PersistentVolumeClaim that follows it after rescheduling. A headless service gives each pod a stable DNS name. Deployments treat pods as interchangeable, which suits stateless apps.
16
Explain stdin, stdout, stderr and what 2>&1 means.
Every process gets three file descriptors: 0 is stdin, 1 is stdout and 2 is stderr. > redirects stdout to a file, 2> redirects errors, and 2>&1 sends stderr to wherever stdout currently points. So command > out.log 2>&1 captures both normal output and errors in one file. Order matters: 2>&1 placed before > out.log would still print errors to the terminal.
17
How do you make your commits and pull requests easy for teammates to review?
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.
18
Write a declarative Jenkinsfile with build, test and deploy stages.
Without locking, both runs read the same state and write conflicting updates, which can corrupt state or create duplicate resources. Use a remote backend with state locking so the second run waits or fails. Better still, run apply only from a CI pipeline on merge to main, so changes are serialised and reviewed. If a lock is stuck after a crash, use terraform force-unlock carefully.
20
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.
21
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.
GitFlow uses long-lived develop and main branches plus feature, release and hotfix branches; it suits scheduled releases but causes big merges. Trunk-based development has everyone merge small changes into main at least daily, with short-lived branches and feature flags to hide unfinished work. It suits continuous delivery and is what high-performing DevOps teams usually prefer, but needs strong automated tests.
23
The kernel OOM killer keeps killing your application. How do you handle it?
Confirm with dmesg or journalctl -k, which shows the OOM message and the killed process. Check whether memory grows over time (a leak) or spikes with load. Set correct heap limits, for example JVM -Xmx below container memory, add swap only as a buffer, and set memory limits so one service cannot starve others. Then profile the app and right-size the instance.
24
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.
25
Compare blue-green, canary and rolling deployments.
Blue-green runs two full environments and switches traffic from old to new at once; rollback is instant but costs double capacity. Rolling replaces instances in batches with no extra environment, but old and new versions run together for a while. Canary sends a small share of traffic, say 5 percent, to the new version and widens it as metrics stay healthy, limiting blast radius.
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.
27
What is the difference between volumes and bind mounts?
A volume is storage managed by Docker under its own directory, created with docker volume create and referenced by name; it is portable and is the recommended way to persist data such as databases. A bind mount maps a specific host path into the container, which is handy for local development hot reload but depends on host directory layout and permissions.
28
How do you configure Prometheus to scrape a target?
# prometheus.yml
global:
scrape_interval: 15s
scrape_configs:
- job_name: node
static_configs:
- targets: ['10.0.1.10:9100', '10.0.1.11:9100']
- job_name: api
metrics_path: /metrics
static_configs:
- targets: ['api.internal:8080']
# validate and reload
promtool check config prometheus.yml
curl -X POST http://localhost:9090/-/reload
Port 9100 is the node exporter default. In Kubernetes, use service discovery or ServiceMonitors instead.
29
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.
30
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.
Tips to crack the Cognizant DevOps interview
Understand the GenC, GenC Next and GenC Elevate tracks so you know which skills and coding level each role expects.
Revise SQL queries, OOP concepts and basic testing terminology since many freshers are placed in development or QA projects.
Read about Cognizant's healthcare and life sciences domain work, which is a large part of its client base.
Keep a one-minute story ready for every project on your CV: problem, your part, tools, result.
Practise the hard questions on this page aloud; Cognizant interviewers usually ask follow-ups on your first answer.
Frequently asked questions
How many rounds are there in the Cognizant DevOps interview?
Candidates usually go through 4 stages: Online assessment (aptitude + reasoning); Coding assessment; Technical interview; HR round. The exact rounds change with the role, team, location and your experience, so confirm the process with the recruiter.
Which topics should I prepare for the Cognizant DevOps interview?
This practice set leans on Docker and Containers (5), Infrastructure as Code (Terraform and Ansible) (5), CI/CD Pipelines (5), Git and Version Control (5). Revise those first, then practise explaining one or two of your own projects end to end, because most Cognizant interviewers ask you to walk through real work.
Are these the exact questions asked at Cognizant?
No. These are curated practice questions that match the skills and difficulty usually tested in it services interviews like Cognizant's. They are not a leaked or verified list of past questions.
Where does Cognizant hire DevOps professionals in India?
Cognizant has large teams in Chennai, Bengaluru, Pune, Hyderabad, Kolkata. Openings and locations change often, so check the Cognizant careers page and filter by city and experience.