Jenkins:
- Self-hosted, highly customizable
- Groovy-based Jenkinsfiles
- Large plugin ecosystem
- Complex to maintain at scale
GitHub Actions:
- Native to GitHub, YAML config
- Free for public repos
- Matrix builds, reusable workflows
GitLab CI:
- Built into GitLab
- Single platform for code + CI/CD
- Auto DevOps features
Interview question: "Compare Jenkins vs GitHub Actions for a -service microservices architecture."
GitHub Actions: simpler, less ops overhead. Jenkins: more control, better for complex pipelines or air-gapped environments.