Continuous Integration and Continuous Deployment is a practice where code changes are automatically built, tested, and deployed to production. CI ensures every commit integrates cleanly with the main codebase. CD automates the release process so tested code reaches users without manual intervention. Together, they transform deployment from a stressful event into a routine, invisible process.
How It Works
A typical CI/CD pipeline has several stages. First, a developer pushes code to a repository. The CI server detects the change and runs the build stage: installing dependencies, compiling code, and generating artifacts. Next comes the test stage: unit tests, integration tests, linting, and type checking run in parallel. If all checks pass, the CD stage deploys to staging for further validation, then promotes to production.
Popular tools include GitHub Actions, GitLab CI, CircleCI, and Jenkins. Cloud platforms offer integrated pipelines: Vercel deploys on push, Railway auto-deploys from Git, and AWS CodePipeline chains build-test-deploy steps.
Cost Optimization
CI/CD costs can grow unexpectedly. Build minutes accumulate, especially on pull requests with many commits. Optimization strategies include caching dependencies between runs, running tests in parallel, using faster build images, and only running relevant tests based on changed files.
GitHub Actions offers generous free tiers for public repositories. For private repositories, self-hosted runners or alternative services (Buildkite, Depot) can reduce costs at scale.
Why It Matters
Without CI/CD, teams accumulate risk. Developers work in isolation for weeks, then face painful merge conflicts and deployment anxiety. Bugs discovered after a large release are harder to trace. Manual deployments are error-prone and slow.
CI/CD inverts this. Small changes deploy frequently, sometimes dozens of times per day. Each deployment carries minimal risk because it contains minimal change. Rollbacks are simple: revert one small commit instead of untangling a month of work.
In Practice
A team using GitHub Actions might configure a workflow that runs on every pull request: TypeScript compilation checks types, Vitest runs 400 tests in 30 seconds, Biome catches style violations, and Playwright runs critical user flows against a preview deployment. Merging to main triggers automatic production deployment with zero downtime.
Pro Tips
Keep pipelines fast; under 10 minutes is ideal. Flaky tests erode confidence and should be fixed or removed immediately. Use branch protection rules requiring CI passage before merge. Implement progressive rollouts (canary deployments) for high-risk changes.
Learn More
- Vercel Deployment – Zero-config CI/CD for Next.js
- AWS Cloud Development – CodePipeline and infrastructure
- Next.js Development – Preview deployments per PR
- SaaS Development – Deployment automation for SaaS