What is continuous deployment?

Continuous Deployment is a software delivery strategy where every code change that passes all stages of the automated CI/CD pipeline (build, testing) is automatically deployed to the production environment without human intervention.

Key differences from Continuous Delivery:

• Continuous Delivery: Changes are ready to be deployed to production, but the deployment process requires an explicit trigger (usually manual).
• Continuous Deployment: Changes are automatically deployed to production after passing all tests.

Advantages:

• Accelerated release of features.
• Shorter feedback cycle.
• Reduced risk through frequent small changes.
• Rapid bug fixes in production.

Prerequisites:

• High level of test automation (unit, integration, acceptance).
• Reliable infrastructure and automated deployment.
• Monitoring and alerting system.
• Ability to quickly rollback changes.

Example steps in a CI/CD pipeline with continuous deployment:

1. Developer commits code to VCS (Git).
2. Build is triggered (Jenkins, GitLab CI, GitHub Actions).
3. Automated tests are run (unit, integration).
4. An artifact is created (Docker image, package).
5. The artifact passes testing in the staging environment.
6. Upon successful completion of all tests, the artifact is automatically deployed to the production environment.
7. Post-deployment checks are performed (health checks, smoke tests).
8. The production environment is monitored for errors and performance.

This requires a high level of trust in automated processes and a mature DevOps culture.