What is CI/CD? Continuous Integration and Continuous Deployment Beginner Tutorial [2025]

What's the scariest thing in software development? Discovering code problems right before launch, the whole team staying up all night for emergency fixes, only to find Bug B after fixing Bug A. This nightmare scenario can actually be avoided through CI/CD.

CI/CD is a core DevOps practice and standard equipment for modern software development teams. It turns code integration and deployment into automated workflows instead of relying on manual operations. This article will take you from concepts to implementation, fully understanding the principles and setup methods of CI/CD.

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What is CI/CD?

CI/CD is a combination of two concepts: CI (Continuous Integration) and CD (Continuous Delivery/Deployment).

What is CI (Continuous Integration)?

Continuous Integration means developers frequently merge code to the main branch, with each merge triggering automated builds and tests.

In traditional development, each developer works on their own branch for weeks or even months before attempting to merge. That's when you often discover code conflicts, and the integration process is painful and time-consuming—this is called "integration hell."

CI's core philosophy is "small steps, fast runs":

• Developers commit code multiple times daily
• Each commit automatically triggers builds and tests
• Problems are discovered immediately and fixed, not accumulated

CD: Continuous Delivery vs Continuous Deployment

CD has two interpretations, often confused:

Continuous Delivery: After code passes all tests, it's always in a deployable state. But actual deployment to production still requires manual approval.

Continuous Deployment: Goes further than continuous delivery—code that passes tests is automatically deployed to production without any manual intervention.

Item	Continuous Delivery	Continuous Deployment
Automation Level	To Staging	To Production
Deployment Approval	Manual required	Fully automatic
Suitable Scenarios	Environments needing review	Highly mature teams
Deployment Frequency	Days to weeks	Hours to days

Most teams implement continuous delivery first, then advance to continuous deployment after building sufficient confidence.

For a deeper understanding of CI/CD's position in the overall DevOps workflow, see our DevOps Complete Guide.

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Why Do We Need CI/CD?

Problem 1: Integration Hell

Teams without CI usually have disaster days on integration day. After developers work separately for weeks, they suddenly try to merge all code together. Conflicts, dependency issues, features affecting each other... solving these problems often takes more time than development itself.

CI's Solution: Integrate multiple times daily, discover and fix problems immediately.

Problem 2: Manual Deployment Risks

"The deployment SOP has 47 steps, I missed step 23."

The biggest problem with manual deployment is unreliability. Even with SOPs, human errors still occur. Worse, each deployment's steps may vary by person, causing environment inconsistencies.

CD's Solution: Write deployment steps as code, executing exactly the same way each time.

Problem 3: Deployment Fear

When deployment becomes complex and risky, teams tend to reduce deployment frequency. Deploying once a month sounds "safer," but actually makes each deployment contain more changes and higher risk.

CI/CD's Solution: Make deployment simple, frequent, and low-risk. Small changes are easier to debug than big ones.

DORA Research Data

According to DORA (DevOps Research and Assessment) research, high-performing teams implementing CI/CD:

• Deploy 208 times more frequently than low-performing teams
• Change lead time is 106 times faster
• Service recovery time is 2,604 times faster
• Change failure rate is 7 times lower

These numbers show CI/CD isn't just a technology choice—it's a key to competitiveness.

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CI/CD Pipeline Design

Pipeline is the core concept of CI/CD. It defines the complete workflow from code commit to deployment, with each phase called a Stage.

Typical Pipeline Structure

┌─────────┐    ┌─────────┐    ┌─────────┐    ┌─────────┐    ┌─────────┐
│  Build  │ -> │  Test   │ -> │   QA    │ -> │ Staging │ -> │  Prod   │
└─────────┘    └─────────┘    └─────────┘    └─────────┘    └─────────┘

Stage 1: Build

This stage's goal is ensuring code can compile successfully.

# Node.js project example
build:
  stage: build
  script:
    - npm ci
    - npm run build
  artifacts:
    paths:
      - dist/

Stage 2: Test

Automatically run various tests to verify code quality.

Test Types:

• Unit Tests: Test smallest functional units, fast execution
• Integration Tests: Test interactions between multiple modules
• End-to-End Tests: Simulate real user operations

test:
  stage: test
  script:
    - npm run test:unit
    - npm run test:integration
  coverage: '/Coverage: \d+.\d+%/'

Stage 3: Security Scan

Modern Pipelines typically include security scanning.

security:
  stage: test
  script:
    - npm audit
    - trivy image myapp:${CI_COMMIT_SHA}

Stage 4: Deploy

Deploy the built application to target environments.

deploy_staging:
  stage: deploy
  script:
    - kubectl apply -f k8s/staging/
  environment:
    name: staging
    url: https://staging.example.com

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CI Continuous Integration Implementation

The key to implementing CI is establishing a fast and reliable feedback mechanism. After developers commit code, they should know the results within minutes.

CI Implementation Key Points

1. Keep Builds Fast

Ideal CI build time is under 10 minutes. If builds are too slow:

• Developers will ignore CI results
• Problems discovered too late, repair costs increase

Acceleration techniques:

• Use parallel testing
• Utilize caching (node_modules, Maven repo)
• Only run affected tests

2. Maintain Stable Tests

The worst situation is flaky tests—same code sometimes passes, sometimes fails. This erodes team trust in CI.

# Strategy for handling flaky tests
test:
  retry:
    max: 2
    when: script_failure

3. Establish Main Branch Protection

Ensure only code passing CI can be merged to the main branch.

# GitHub Branch Protection Rules
- Require status checks to pass
- Require branches to be up to date
- Include administrators

CI Implementation Example: GitHub Actions

name: CI Pipeline

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Run linter
        run: npm run lint

      - name: Run tests
        run: npm run test -- --coverage

      - name: Build
        run: npm run build

      - name: Upload coverage
        uses: codecov/codecov-action@v3

Automated Testing Strategy

Testing Pyramid principle:

        /\
       /  \   E2E Tests (few)
      /----\
     /      \  Integration Tests (moderate)
    /--------\
   /          \ Unit Tests (many)
  /__________\

• 70% Unit Tests: Fast, stable, covers all logic
• 20% Integration Tests: Verify module interactions
• 10% E2E Tests: Verify critical user flows

Want to build automated testing workflows but don't know where to start? Schedule an architecture consultation and let us help design an appropriate testing strategy.

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CD Continuous Deployment Implementation

CD's challenge is how to safely deploy new versions to production without affecting users.

Deployment Strategy Comparison

Rolling Update

Gradually replace old version Pods, no extra resources needed.

# Kubernetes Rolling Update
spec:
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0

Pros: High resource efficiency, zero downtime Cons: Slower rollback, old and new versions coexist temporarily

Blue-Green Deployment

Maintain two identical environments simultaneously, switch traffic instantly.

         ┌─────────────┐
         │   Router    │
         └──────┬──────┘
                │
    ┌───────────┼───────────┐
    │           │           │
    ▼           │           ▼
┌───────┐       │       ┌───────┐
│ Blue  │       │       │ Green │
│ (v1)  │◄──────┘       │ (v2)  │
└───────┘               └───────┘
   Old                    New

Pros: Instant rollback, test complete environment Cons: Requires double resources

Canary Deployment

First direct small amount of traffic to new version, gradually increase after observing no issues.

# Istio Canary configuration
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
spec:
  http:
    - route:
      - destination:
          host: myapp
          subset: v1
        weight: 90
      - destination:
          host: myapp
          subset: v2
        weight: 10

Pros: Lowest risk, real-time monitoring Cons: Complex configuration, requires traffic management

CD Implementation Example: GitLab CI/CD

stages:
  - build
  - test
  - deploy_staging
  - deploy_production

deploy_staging:
  stage: deploy_staging
  script:
    - kubectl apply -f k8s/staging/
  environment:
    name: staging
    url: https://staging.example.com
  only:
    - develop

deploy_production:
  stage: deploy_production
  script:
    - kubectl apply -f k8s/production/
  environment:
    name: production
    url: https://www.example.com
  when: manual  # Manual trigger
  only:
    - main

Rollback Strategy

No matter how perfect the deployment strategy, you need a rollback plan.

# Kubernetes rollback
kubectl rollout undo deployment/myapp

# View deployment history
kubectl rollout history deployment/myapp

# Rollback to specific version
kubectl rollout undo deployment/myapp --to-revision=2

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CI/CD Tool Comparison

There are many CI/CD tools available—choose based on your team's existing tech stack and needs.

Mainstream Tool Comparison Table

Tool	Type	Features	Best For
GitHub Actions	SaaS	Deep GitHub integration	GitHub users
GitLab CI/CD	SaaS/Self-hosted	Complete DevOps platform	Need integrated solution
Jenkins	Self-hosted	High flexibility, many plugins	Need high customization
Azure Pipelines	SaaS	Azure ecosystem integration	Microsoft tech stack
CircleCI	SaaS	Fast, simple setup	Fast iteration teams

GitHub Actions

Pros:

• Seamless GitHub integration
• Marketplace has many ready-made Actions
• Intuitive YAML configuration

Limitations:

• Public repos free, private repos have minute limits
• Complex workflow setup can be tedious

GitLab CI/CD

Pros:

• Built-in CI/CD, no extra setup needed
• Complete DevOps platform
• Can self-host Runners

Limitations:

• Steeper learning curve
• Self-hosting requires maintenance costs

For detailed tool comparisons and selection recommendations, see DevOps Tools Complete Guide. If your team uses Microsoft tech stack, also see Azure DevOps Complete Tutorial.

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CI/CD Implementation Example

Here's a complete Node.js project CI/CD example.

Project Structure

myapp/
├── src/
├── tests/
├── Dockerfile
├── k8s/
│   ├── deployment.yaml
│   └── service.yaml
└── .github/
    └── workflows/
        └── cicd.yaml

Complete Pipeline Example

name: CI/CD Pipeline

on:
  push:
    branches: [main, develop]
  pull_request:
    branches: [main]

env:
  REGISTRY: ghcr.io
  IMAGE_NAME: ${{ github.repository }}

jobs:
  # Stage 1: Build and Test
  build-and-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Install dependencies
        run: npm ci

      - name: Run linter
        run: npm run lint

      - name: Run unit tests
        run: npm run test:unit -- --coverage

      - name: Run integration tests
        run: npm run test:integration

      - name: Build application
        run: npm run build

      - name: Upload build artifacts
        uses: actions/upload-artifact@v3
        with:
          name: build
          path: dist/

  # Stage 2: Build Docker Image
  build-image:
    needs: build-and-test
    runs-on: ubuntu-latest
    if: github.ref == 'refs/heads/main'

    outputs:
      image-tag: ${{ steps.meta.outputs.tags }}

    steps:
      - uses: actions/checkout@v4

      - name: Download build artifacts
        uses: actions/download-artifact@v3
        with:
          name: build
          path: dist/

      - name: Log in to Container Registry
        uses: docker/login-action@v3
        with:
          registry: ${{ env.REGISTRY }}
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build and push Docker image
        uses: docker/build-push-action@v5
        with:
          context: .
          push: true
          tags: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }}

  # Stage 3: Deploy to Staging
  deploy-staging:
    needs: build-image
    runs-on: ubuntu-latest
    environment:
      name: staging
      url: https://staging.example.com

    steps:
      - uses: actions/checkout@v4

      - name: Deploy to Staging
        run: |
          kubectl set image deployment/myapp \
            myapp=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }} \
            --namespace=staging

  # Stage 4: Deploy to Production (Manual Trigger)
  deploy-production:
    needs: deploy-staging
    runs-on: ubuntu-latest
    environment:
      name: production
      url: https://www.example.com

    steps:
      - uses: actions/checkout@v4

      - name: Deploy to Production
        run: |
          kubectl set image deployment/myapp \
            myapp=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ github.sha }} \
            --namespace=production

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CI/CD Best Practices

1. Pipeline as Code

Store Pipeline definitions in version control to enjoy all benefits of code management: version history, Code Review, branch management.

2. Environment Consistency

Use Docker to ensure consistent build environments.

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY dist/ ./dist/
CMD ["node", "dist/index.js"]

3. Secrets Management

Never put secrets in code or Pipeline configuration.

# Correct approach: Use Secrets
env:
  DATABASE_URL: ${{ secrets.DATABASE_URL }}
  API_KEY: ${{ secrets.API_KEY }}

4. Build Meaningful Artifacts

Retain build outputs for debugging and auditing.

- name: Upload test results
  uses: actions/upload-artifact@v3
  if: always()
  with:
    name: test-results
    path: test-results/
    retention-days: 30

5. Monitor Pipeline Performance

Track Pipeline execution time, optimize regularly.

Metric	Recommended Value	Description
Total Build Time	< 10 minutes	Over this reduces development efficiency
Test Coverage	> 80%	Below this, hard to ensure quality
Pipeline Success Rate	> 95%	Below this indicates instability issues

CI/CD is also a core skill in the DevOps Learning Roadmap. After establishing CI/CD, the next step is usually building a monitoring system—see DevOps Monitoring Guide.

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FAQ

What's the relationship between CI/CD and DevOps?

CI/CD is a core component of DevOps practices. DevOps is a culture and methodology, while CI/CD is the specific technical practice for achieving DevOps automated delivery goals.

How long does it take to build CI/CD?

Basic Pipeline can be set up in a few days. But building a mature CI/CD workflow with complete testing, security scanning, and multi-environment deployment typically requires several months of continuous iteration.

Do small teams need CI/CD?

Yes. In fact, small teams need automation even more to improve efficiency. Free plans from tools like GitHub Actions and GitLab CI/CD are already sufficient for small teams.

Is Continuous Deployment safe?

The premise of continuous deployment is having sufficient automated testing and monitoring. If test coverage is complete and monitoring is in place, continuous deployment is actually safer than manual deployment because it eliminates human error.

What's the difference between CI/CD and GitOps?

CI/CD is the workflow for automated building and deployment. GitOps is a practice that makes Git the Single Source of Truth, where all changes are triggered through Git commits. GitOps can be seen as an advanced practice of CD.

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Conclusion

CI/CD is the infrastructure of modern software development. It's not just a technology tool choice—it's an embodiment of team development culture.

Value of Implementing CI/CD:

1. Fast Feedback: Problems discovered early, fixed early
2. Reduced Risk: Small steps are safer than big explosions
3. Increased Efficiency: Automation reduces repetitive work
4. Build Confidence: Reliable processes let teams focus on creating value

Starting to build CI/CD doesn't need to be perfect from day one. You can start with the most basic automated testing, gradually adding builds, deployments, and monitoring. What matters is continuous improvement, making the Pipeline increasingly robust.

Want to build efficient CI/CD workflows in your team? Schedule an architecture consultation—we'll help you design the most suitable Pipeline architecture, from build to deployment in one go.