CI/CD Pipelines Explained: What They Are and Why Your Team Probably Needs One

CI (Continuous Integration) is the practice of automatically building and testing code whenever changes are pushed to a shared repository. The goal is to detect integration problems early — before a branch has diverged too far to merge cleanly, and before broken code reaches teammates. CD has two interpretations: Continuous Delivery means code is always in a deployable state and deployment is automated but may require manual approval. Continuous Deployment means every change that passes tests is automatically deployed to production without manual intervention. Most teams practice CI and Continuous Delivery. Fully automated Continuous Deployment is less common and requires high confidence in automated testing.

A minimal CI pipeline for a web application: dependency installation (npm ci, pip install), linting (ESLint, Flake8), type checking (tsc --noEmit for TypeScript), unit tests, integration tests if applicable, and build (to verify the build doesn't fail). More mature pipelines add: security scanning (dependency vulnerability checks like npm audit), code coverage thresholds, end-to-end tests (Cypress, Playwright), Docker build to verify the container builds, and performance budgets. The goal is catching any change that would break the application or degrade quality before it's merged to the main branch.

Deployment strategies control how new code is released to users. Blue-green deployment runs two identical production environments — traffic switches between them during deployments, enabling instant rollback. Rolling deployment gradually replaces old instances with new ones over time. Canary deployment routes a small percentage of traffic to the new version first, monitoring for problems before full rollout. Feature flags decouple deployment from release — code ships to all users but features are toggled on for specific users or percentages. For most teams, rolling deployments via Docker/Kubernetes with feature flags for riskier changes is a practical starting point. Blue-green adds infrastructure cost but makes rollback trivial.