DevOps Interview Questions

Describe the complete CI/CD pipeline you have implemented in your projects. Walk through every stage from code commit to production deployment, including linting, unit tests, build, artifact storage, staging deploy, integration tests, and release gates.

If a critical issue is found in production, what steps would you take to resolve it quickly? Walk through: immediate triage, deciding between hotfix vs rollback, creating a hotfix branch, fast-track CI pipeline, communication protocol, and post-mortem.

What is the difference between ENTRYPOINT and CMD in Docker? Explain with examples how they interact when both are specified, and how CMD can be overridden at runtime while ENTRYPOINT cannot easily be replaced.

What are the key steps involved in building a Docker image? Explain each Dockerfile instruction (FROM, RUN, COPY, WORKDIR, EXPOSE, CMD), multi-stage builds for smaller images, layer caching best practices, and how to scan images for vulnerabilities.

What stages do you generally include in a Jenkins pipeline to ensure code quality? Walk through each stage: checkout, static analysis (SonarQube/ESLint), unit tests with coverage thresholds, security scanning, build, and artifact publishing.

Explain the difference between Declarative and Scripted pipelines in Jenkins. When would you choose one over the other? Show a code snippet illustrating the structural difference.

Which Git branching strategy do you follow — GitFlow or trunk-based development — and why? Compare release cadence, merge complexity, hotfix handling, and suitability for CI/CD pipelines.

How do you pass environment variables during Docker build and runtime? Compare ARG (build-time) vs ENV (runtime), how to use --build-arg and --env-file, the security implications of baking secrets into layers, and safer alternatives like Docker secrets.

What are Jenkins Shared Libraries and how are they used in Jenkinsfiles? Explain the directory structure, how to import them, and how they help enforce consistency across multiple pipelines in a large organisation.

What is a webhook and how is it used in CI/CD automation? Explain how a GitHub webhook triggers a Jenkins job, the payload structure, how to secure it with a secret token, and how to debug failed webhook deliveries.

How can Jenkins pipelines be created and triggered automatically? Explain pipeline-as-code with Jenkinsfile in SCM, multibranch pipelines that auto-discover branches, Organization Folders for GitHub orgs, and automatic triggering via webhooks vs SCM polling.

How do you prevent breaking the release branch during development? Discuss branch protection rules, required PR reviews, mandatory status checks, feature flags, and how to use a staging environment as a gate before merging to release.