CI/CD¶

CI (Continuous Integration): Developers merge code frequently, each merge triggers automated build + tests. CD (Continuous Delivery): Code is always deployable; release requires manual approval. Continuous Deployment: Every change that passes tests is automatically deployed to production. Tools: Jenkins, GitHub Actions, GitLab CI, CircleCI. Key practices: automated testing, infrastructure as code, feature flags.

Key Concepts¶

Deep Dive: CI/CD Pipeline

Code Push → Build → Unit Tests → Integration Tests
                                      ↓
Production ← Staging ← Deploy ← Artifact Store

GitHub Actions example:

name: CI/CD Pipeline
on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  build:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v4
    - uses: actions/setup-java@v4
      with:
        java-version: '21'
        distribution: 'temurin'
    - run: mvn clean verify
    - run: docker build -t my-app:${{ github.sha }} .

  deploy:
    needs: build
    if: github.ref == 'refs/heads/main'
    runs-on: ubuntu-latest
    steps:
    - run: kubectl set image deployment/my-app my-app=my-app:${{ github.sha }}

Deep Dive: Deployment Strategies

Strategy	Description	Risk	Rollback
Rolling	Gradually replace pods	Low	Slow
Blue-Green	Two environments, switch traffic	Low	Instant
Canary	Route small % traffic to new version	Very low	Instant
Recreate	Stop old, start new	High (downtime)	Slow

Deep Dive: Best Practices

Automate everything — build, test, deploy
Fast feedback — tests should run in minutes, not hours
Small, frequent changes — easier to debug and rollback
Feature flags — decouple deployment from release
Branch protection — require PR reviews and passing tests
Immutable artifacts — build once, deploy everywhere

Common Interview Questions

What is the difference between CI and CD?
What are deployment strategies? Explain Blue-Green.
How do you handle database migrations in CI/CD?
What is a feature flag?
How do you handle rollbacks?
What CI/CD tools have you used?