CI/CD Pipelines¶

By Sameer Alam · Updated 14 September 2026

What You'll Learn¶

• How a change flows through test, build, image, registry, and deploy stages
• How GitHub Actions, GitLab CI, Jenkins, and ArgoCD map onto those stages
• The difference between push-based deployment and GitOps
• A reading order through the section

CI/CD is the automation backbone of modern software delivery. Continuous Integration (CI) builds and tests every change as soon as it is pushed. Continuous Delivery/Deployment (CD) packages that change — usually as a container image — and ships it to an environment automatically.

This section is a practical, tool-by-tool deep dive. Every page includes installation and setup guidance, real YAML you can copy, and diagrams of how the pieces connect.

The Big Picture¶

Every CI/CD pipeline, regardless of tool, is a variation of this flow:

flowchart LR
    DEV[Developer<br>git push] --> CI[CI Pipeline<br>lint + unit tests]
    CI --> BUILD[Build Artifact<br>JAR / wheel]
    BUILD --> IMG[Docker Image<br>multi-stage build]
    IMG --> REG[(Container Registry<br>GHCR / Docker Hub / GitLab)]
    REG --> CD[CD Stage<br>deploy job or GitOps]
    CD --> ENV[Environment<br>VM / Kubernetes / Cloud]
    classDef dev fill:#fef3c7,stroke:#d97706,color:#78350f
    classDef ci fill:#dbeafe,stroke:#2563eb,color:#172554
    classDef img fill:#ede9fe,stroke:#7c3aed,color:#3b0764
    classDef deploy fill:#dcfce7,stroke:#16a34a,color:#14532d
    class DEV dev
    class CI,BUILD ci
    class IMG,REG img
    class CD,ENV deploy

The stages map to concrete tool features:

Choosing a Tool¶

flowchart TD
    Q1{Where is<br>your code?} -->|GitHub| GHA[GitHub Actions]
    Q1 -->|GitLab| GL[GitLab CI/CD]
    Q1 -->|Self-hosted /<br>legacy needs| JK[Jenkins]
    GHA --> Q2{Deploying to<br>Kubernetes?}
    GL --> Q2
    JK --> Q2
    Q2 -->|Yes| ARGO[Add ArgoCD<br>for GitOps CD]
    Q2 -->|No| DIRECT[Deploy from<br>the pipeline]
    classDef q fill:#fef3c7,stroke:#d97706,color:#78350f
    classDef tool fill:#dbeafe,stroke:#2563eb,color:#172554
    classDef gitops fill:#dcfce7,stroke:#16a34a,color:#14532d
    class Q1,Q2 q
    class GHA,GL,JK,DIRECT tool
    class ARGO gitops

• GitHub Actions — zero infrastructure to start, huge marketplace of reusable actions, free minutes for public repos. The default choice if your code lives on GitHub.
• GitLab CI/CD — a single application for repos, pipelines, and a container registry. Excellent for self-hosted setups.
• Jenkins — self-hosted, plugin-driven, infinitely customizable. Common in enterprises with existing investment. See the Jenkins guide.
• ArgoCD — not a CI tool at all; a Kubernetes GitOps controller that continuously reconciles your cluster with Git.

Section Contents¶

Common Mistakes¶

• Deploying from CI with long-lived cloud credentials instead of short-lived OIDC federation.
• Rebuilding the image for each environment instead of promoting one tested artifact.
• Letting pipelines deploy without a test gate, or letting flaky tests be retried until green.
• Deploying mutable tags like latest, so nobody knows which build is running.
• One monolithic pipeline file that nobody dares to change.

Interview Questions¶

• What's the difference between continuous delivery and continuous deployment?
• Compare push-based deployment with GitOps pull-based deployment.
• How would you choose between GitHub Actions, GitLab CI, and Jenkins for a new team?

Further Reading¶

• GitHub Actions Documentation
• GitLab CI/CD Documentation
• Jenkins Documentation

Next¶

Continue to GitHub Actions Deep Dive. If your team hasn't settled on a branching model yet, read Branching Strategies first.