What Is CI/CD: Continuous Integration and Delivery Explained

CI/CD in plain words

CI/CD is a practice where automation, not a person working from memory, moves code from the developer to users. Every change goes through the same conveyor — the pipeline: build, tests, checks, deployment.

The acronym covers three ideas:

• Continuous Integration (CI) — developers merge changes into a shared branch often, and every change automatically triggers a build and tests. The goal is to learn about a breakage in minutes, not a week later.
• Continuous Delivery — every version that passes the checks is ready to release. Going to production is one button, and a person makes the call.
• Continuous Deployment — one step further: a version that passes all checks goes to production automatically, with no manual approval.

Delivery vs deployment

You almost always start with CI and continuous delivery. Fully automatic deployment is the next step, once the team trusts its tests.

A typical pipeline, step by step

1. Trigger. A developer pushes code or opens a pull request.
2. Build. Dependencies are installed, the project is compiled, a Docker image is built.
3. Static checks. Linters, formatting, type checks, scanning dependencies for known vulnerabilities.
4. Tests. Unit tests, then integration tests. If something fails, the pipeline stops and the author is notified.
5. Artifact. The finished build is stored with a unique version, for example an image tagged with the commit hash.
6. Deploy to staging. The same build goes to a test environment that resembles production.
7. Acceptance checks. Automated scenario tests or a manual review.
8. Deploy to production. By button or automatically, ideally gradually.
9. Monitoring and rollback. If metrics get worse, you quickly return to the previous version.

A minimal pipeline in GitHub Actions:

name: ci
on:
  pull_request:
  push:
    branches: [main]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-node@v4
        with:
          node-version: 20
      - run: npm ci
      - run: npm run lint
      - run: npm test

Similar pipelines are built in GitLab CI, Jenkins and other systems — the principle is the same.

What it gives the business

• Faster feature delivery. A finished feature reaches users as soon as it passes the checks instead of waiting for a "big release".
• Lower risk. Small, frequent releases are easier to verify and roll back than rare, large ones.
• Less manual work. Nobody copies files to a server by hand or skips a step from the instructions.
• Predictability. Every version is built the same way, and you always know what runs in production.
• No single point of knowledge. The release process lives in code, not in one developer's head.

Common mistakes when adopting CI/CD

• A pipeline without tests. Automatically deploying unchecked code just ships bugs faster.
• A slow pipeline. If checks take too long, people start bypassing them. Cache dependencies and run steps in parallel.
• Flaky tests. Tests that fail at random teach the team to ignore a red status.
• Secrets in the repository. Passwords and keys belong in protected CI variables, not in code.
• Different builds for staging and production. Production should get the exact artifact that passed the checks.
• No rollback plan. Rolling back should be as simple as deploying.

Syntax reference: GitHub Actions documentation.