Putting It All Together

Layers:

Beyond:

• Reusable workflows: uses: org/repo/.github/workflows/x.yml@v1 to share pipelines across repos.
• Environments + approvals: prod requires manual click-to-deploy.
• Container jobs: container: node:20. Each step runs in that container.
• Workflow concurrency: concurrency: deploy-prod prevents overlapping runs.
• Reusable actions: write your own. JavaScript, Docker, or composite (multi-step) actions.
• Build matrices conditional on changed files: only run frontend tests if frontend changed.

Real production CI involves:

• Cache strategy (avoid re-downloading deps every time)
• Parallel test sharding (split test suite across N runners)
• Test result reporting (JUnit XML → UI)
• Code coverage tracking
• Performance regression detection
• Deploy approvals + rollback

Where you've seen CI:

• GitHub Actions: ubiquitous now
• GitLab CI: built-in for GitLab repos
• Jenkins: legacy enterprise but still common
• CircleCI / Buildkite / Drone: SaaS variants
• Argo Workflows: Kubernetes-native CI/CD

You now understand the full pipeline.