Top 35 CI/CD Interview Questions & Answers 2025

CI (Continuous Integration): frequently merge code to main branch, automated builds and tests catch issues early. CD (Continuous Delivery/Deployment): automate release process to any environment. Benefits: faster feedback, reduced risk, consistent quality, frequent releases. CI catches integration issues; CD ensures reliable deployments. Foundation of DevOps practices.

Blue-Green: two identical environments, switch traffic instantly. Canary: gradual rollout to subset of users. Rolling: replace instances incrementally. A/B Testing: feature comparison with metrics. Feature flags: toggle features without deployment. Recreate: stop old, start new (downtime). Choose based on: risk tolerance, rollback needs, infrastructure capabilities.

Stages: (1) Source (trigger on commit), (2) Build (compile, dependencies), (3) Test (unit, integration, e2e), (4) Security scan (SAST, dependencies), (5) Artifact creation, (6) Deploy to staging, (7) Acceptance tests, (8) Deploy to production. Also: notifications, rollback capability, environment promotion, audit trails. Fail fast at earlier stages.

Never store secrets in code or pipeline files. Solutions: (1) CI/CD secret variables (masked in logs), (2) External secret managers (Vault, AWS Secrets Manager), (3) Environment-specific secrets, (4) Short-lived credentials (OIDC). Best practices: rotate regularly, audit access, principle of least privilege, scan for accidental commits.

Jenkins: open-source, highly customizable, plugins ecosystem, self-hosted. GitHub Actions: native GitHub integration, YAML workflows, marketplace actions. GitLab CI: integrated with GitLab, Auto DevOps features. CircleCI: cloud-native, fast, good Docker support. AWS CodePipeline: AWS integration, managed service. Choose based on: existing tools, hosting preference, team expertise.