44 CI/CD interview questions with answers

All CI/CD interview questions

• What is CI/CD? What is the difference between CI and CD?

• What is GitHub Actions? What is the structure of a workflow file?

• What are Blue-Green deployment and Canary deployment?

• What is a CI/CD pipeline? What steps does a typical frontend pipeline include?

• How do GitLab CI, Jenkins, and CircleCI compare to GitHub Actions?

• What is GitOps? How do ArgoCD and Flux work?

• How do you design a fail-fast CI pipeline that uses time efficiently?

• How do you manage secrets in CI/CD securely?

• Rolling, recreate, canary, blue-green deploys: when do you use each?

• Build artifacts, immutable images, and semantic versioning in CI/CD?

• Trunk-based development vs Git Flow in modern CI/CD?

• Pre-commit hooks, lint-staged, husky — client-side vs server-side CI gates?

• What is chaos engineering, and why deliberately inject failures into a system?

• Where should image vulnerability scanning sit in CI, and what do you do when the scanner reports hundreds of CVEs?

• How do you design a multi-stage CI/CD pipeline? Which jobs run in parallel and which must be sequential?

• How should you key a dependency cache in CI? Why hash the lockfile?

• How do you pass build output from one job to another? How do artifacts differ from caches?

• What is a matrix build? When do you need one, and how do you keep it from wasting time?

• A 30-minute test suite is blocking the pipeline. How do you parallelize it?

• The pipeline goes red occasionally and passes on rerun. How do you deal with flaky tests?

• How do you block a merge when lint / typecheck / coverage fail? How should the gate be configured?

• How do you make sure a CI secret never leaks into the logs?

• The same artifact is deployed to dev / staging / production — how do you handle per-environment configuration?

• How do feature flags decouple deploy from release? What are the trade-offs?

• You deploy to production and find a serious bug. How do you roll back within minutes?

• Where do database migrations belong in the pipeline — before or after deploying code? How do you avoid downtime?

• Why use OIDC instead of long-lived access keys for CI deployments to the cloud? How does it work?

• What are the risks of running CI on pull requests from forks? How do you make it safe?

• In a monorepo with many services, how do you run only the jobs affected by a change?

• Production deploys need approval, notification, and an audit trail. How do you build that into the pipeline?

• What question does each of logs, metrics and traces answer? Which do you look at first during an incident?

• What is structured logging? How does a correlation (request) id work across services?

• How do you pick the right log level? What must never be written to logs?

• What should a service dashboard contain? How do you arrange it so an on-caller can use it at 3am?

• Logging costs exploded in production. How do you cut them and still be able to debug?

• Why should `user_id` (or `request_id`) never be a metric label? What is cardinality?

• What are the RED and USE methods? When do you use each?

• What mechanism stitches a trace across services? How do you keep the trace through a message queue?

• What problem does OpenTelemetry solve? What are its components?

• Why alert on symptoms rather than causes? Give a concrete example.

• What is alert fatigue? How do you reduce it? How does multi-window multi-burn-rate alerting work?

• What decisions does an error budget drive? Can an SLO be 100%?

• How does handling a production incident go? Why does mitigation come before fixing the root cause?

• What is a blameless postmortem? What does a good one contain?