Learning Crossplane

A comprehensive learning resource for Crossplane v2.1+, the cloud-native control plane framework for building platforms without writing code.

References

📚 Table of Contents

About This Repository
What is Crossplane
Prerequisites
Directory Structure
Getting Started
Learning Path
Key Concepts
Hands-On Labs
Best Practices
Resources
Contributing
License

About This Repository

This repository serves as a structured learning resource for mastering Crossplane, covering everything from basic concepts to advanced composition functions and production deployments. It includes practical examples, hands-on labs, and real-world patterns for building cloud-native control planes.

Current Crossplane Version Coverage: v2.1 (November 2025) Status: CNCF Graduated Project (October 28, 2025)

What is Crossplane

Crossplane is a framework for building cloud-native control planes without needing to write code. It provides:

Universal Control Plane: Orchestrate applications and infrastructure across any cloud
Declarative API: Define resources using familiar Kubernetes patterns
Extensible Backend: Build control planes using providers and composition functions
Configurable Frontend: Control the schema of your declarative API
Platform Engineering: Enable self-service infrastructure for development teams

Key Features in Crossplane v2.1

Namespaced Composite Resources: XRs are now namespaced by default
Simplified Architecture: No more need for Claims abstraction
Enhanced Composition Functions: Advanced templating with Python, Go, KCL, and more
Better Application Support: First-class support for managing apps alongside infrastructure
Improved Developer Experience: Streamlined workflows and better tooling

Prerequisites

Required Knowledge

Basic understanding of Kubernetes concepts (Pods, Services, Deployments)
Familiarity with YAML syntax
Command-line interface (CLI) experience
Basic cloud infrastructure concepts

Required Tools

Kubernetes Cluster: v1.25+ (can use kind, minikube, or cloud provider)
kubectl: v1.25+ (Installation Guide)
Crossplane CLI: v1.17+ (Installation Guide)
Docker: v24+ (for testing composition functions)
Helm: v3.0+ (for Crossplane installation)

Optional Tools

k9s: Terminal UI for Kubernetes
yq: YAML processor
jq: JSON processor
VS Code: With Kubernetes and YAML extensions

Directory Structure

learning-crossplane/
│
├── README.md                          # This file
├── LICENSE                            # MIT License
├── .gitignore                        # Git ignore patterns
│
├── 01-fundamentals/                  # Crossplane fundamentals
│   ├── README.md                     # Fundamentals overview
│   ├── 01-installation/              # Installation methods
│   │   ├── helm-install.yaml
│   │   ├── helm-values.yaml
│   │   └── verify-installation.sh
│   ├── 02-providers/                 # Provider basics
│   │   ├── provider-aws.yaml
│   │   ├── provider-azure.yaml
│   │   ├── provider-gcp.yaml
│   │   ├── provider-kubernetes.yaml
│   │   └── provider-config.yaml
│   ├── 03-managed-resources/         # Managed resources
│   │   ├── s3-bucket.yaml
│   │   ├── rds-instance.yaml
│   │   ├── vpc.yaml
│   │   └── README.md
│   └── 04-basic-concepts/            # Core concepts
│       ├── crds.yaml
│       ├── custom-resources.yaml
│       └── resource-lifecycle.md
│
├── 02-compositions/                  # Composition fundamentals
│   ├── README.md                     # Composition overview
│   ├── 01-xrd-basics/                # XRD fundamentals
│   │   ├── simple-xrd.yaml
│   │   ├── namespaced-xrd.yaml
│   │   ├── cluster-scoped-xrd.yaml
│   │   └── schema-definition.yaml
│   ├── 02-basic-compositions/        # Basic compositions
│   │   ├── patch-and-transform.yaml
│   │   ├── resource-templates.yaml
│   │   └── composition-metadata.yaml
│   ├── 03-composite-resources/       # Working with XRs
│   │   ├── namespaced-xr.yaml
│   │   ├── cluster-xr.yaml
│   │   ├── xr-status.yaml
│   │   └── README.md
│   └── 04-v2-migration/              # v1 to v2 migration
│       ├── legacy-composition.yaml
│       ├── v2-composition.yaml
│       └── migration-guide.md
│
├── 03-composition-functions/         # Composition functions
│   ├── README.md                     # Functions overview
│   ├── 01-patch-and-transform/       # P&T function
│   │   ├── function-install.yaml
│   │   ├── simple-transform.yaml
│   │   ├── conditional-patching.yaml
│   │   └── examples/
│   ├── 02-function-pipeline/         # Function pipelines
│   │   ├── pipeline-composition.yaml
│   │   ├── multi-function.yaml
│   │   └── function-chaining.yaml
│   ├── 03-templating-functions/      # Template-based functions
│   │   ├── go-templating/
│   │   │   ├── function-config.yaml
│   │   │   └── template-examples.yaml
│   │   ├── kcl-function/
│   │   │   ├── function-install.yaml
│   │   │   └── kcl-examples/
│   │   └── helm-function/
│   │       └── helm-composition.yaml
│   ├── 04-custom-functions/          # Writing custom functions
│   │   ├── python-function/
│   │   │   ├── function.py
│   │   │   ├── Dockerfile
│   │   │   ├── requirements.txt
│   │   │   └── README.md
│   │   ├── go-function/
│   │   │   ├── main.go
│   │   │   ├── go.mod
│   │   │   ├── Dockerfile
│   │   │   └── README.md
│   │   └── function-testing/
│   │       ├── test-inputs.yaml
│   │       └── render-tests.sh
│   └── 05-advanced-patterns/         # Advanced function patterns
│       ├── conditional-logic.yaml
│       ├── loops-iteration.yaml
│       ├── external-data.yaml
│       └── error-handling.yaml
│
├── 04-real-world-examples/           # Production-ready examples
│   ├── README.md                     # Examples overview
│   ├── 01-database-platform/         # Database self-service
│   │   ├── xrd/
│   │   │   └── database-xrd.yaml
│   │   ├── compositions/
│   │   │   ├── postgres-composition.yaml
│   │   │   ├── mysql-composition.yaml
│   │   │   └── mongodb-composition.yaml
│   │   ├── claims/
│   │   │   └── sample-database.yaml
│   │   └── README.md
│   ├── 02-application-platform/      # App deployment platform
│   │   ├── xrd/
│   │   │   └── app-xrd.yaml
│   │   ├── composition/
│   │   │   └── app-composition.yaml
│   │   ├── examples/
│   │   │   ├── frontend-app.yaml
│   │   │   └── backend-app.yaml
│   │   └── README.md
│   ├── 03-network-platform/          # Network infrastructure
│   │   ├── vpc-xrd.yaml
│   │   ├── vpc-composition.yaml
│   │   ├── subnet-composition.yaml
│   │   └── security-group-composition.yaml
│   ├── 04-observability-platform/    # Monitoring & logging
│   │   ├── monitoring-xrd.yaml
│   │   ├── prometheus-composition.yaml
│   │   ├── grafana-composition.yaml
│   │   └── loki-composition.yaml
│   └── 05-multi-cloud/               # Multi-cloud patterns
│       ├── provider-selection.yaml
│       ├── aws-composition.yaml
│       ├── azure-composition.yaml
│       └── gcp-composition.yaml
│
├── 05-security/                      # Security best practices
│   ├── README.md                     # Security overview
│   ├── 01-rbac/                      # Access control
│   │   ├── roles.yaml
│   │   ├── rolebindings.yaml
│   │   └── service-accounts.yaml
│   ├── 02-secrets-management/        # Secrets handling
│   │   ├── external-secrets.yaml
│   │   ├── sealed-secrets.yaml
│   │   └── vault-integration.yaml
│   ├── 03-policy-enforcement/        # Policy as code
│   │   ├── opa-policies/
│   │   ├── kyverno-policies/
│   │   └── admission-control.yaml
│   └── 04-compliance/                # Compliance patterns
│       ├── audit-logging.yaml
│       └── compliance-checks.yaml
│
├── 06-operations/                    # Operational excellence
│   ├── README.md                     # Operations overview
│   ├── 01-monitoring/                # Monitoring setup
│   │   ├── prometheus-rules.yaml
│   │   ├── grafana-dashboards/
│   │   └── alerts.yaml
│   ├── 02-troubleshooting/           # Debug procedures
│   │   ├── debug-commands.sh
│   │   ├── common-issues.md
│   │   └── logs-analysis.md
│   ├── 03-backup-restore/            # DR procedures
│   │   ├── backup-strategy.md
│   │   └── restore-procedures.md
│   ├── 04-upgrades/                  # Upgrade strategies
│   │   ├── upgrade-checklist.md
│   │   ├── rollback-plan.md
│   │   └── version-migration.yaml
│   └── 05-performance/               # Performance tuning
│       ├── scaling-config.yaml
│       └── optimization-guide.md
│
├── 07-ci-cd-integration/             # CI/CD pipelines
│   ├── README.md                     # CI/CD overview
│   ├── 01-gitops/                    # GitOps workflows
│   │   ├── argocd/
│   │   │   ├── application.yaml
│   │   │   └── app-of-apps.yaml
│   │   └── flux/
│   │       ├── kustomization.yaml
│   │       └── helmrelease.yaml
│   ├── 02-github-actions/            # GitHub workflows
│   │   ├── validate-composition.yaml
│   │   ├── test-functions.yaml
│   │   └── deploy-crossplane.yaml
│   ├── 03-gitlab-ci/                 # GitLab pipelines
│   │   └── .gitlab-ci.yaml
│   └── 04-testing/                   # Automated testing
│       ├── composition-tests/
│       ├── function-tests/
│       └── integration-tests/
│
├── 08-advanced-topics/               # Advanced scenarios
│   ├── README.md                     # Advanced topics overview
│   ├── 01-custom-providers/          # Building providers
│   │   ├── provider-template/
│   │   └── upjet-provider/
│   ├── 02-function-development/      # Advanced function dev
│   │   ├── sdk-usage/
│   │   ├── grpc-implementation/
│   │   └── optimization-patterns/
│   ├── 03-webhooks/                  # Validation webhooks
│   │   ├── admission-webhook.yaml
│   │   └── validation-logic.go
│   └── 04-event-driven/              # Event-driven patterns
│       ├── triggers.yaml
│       └── event-handlers/
│
├── 09-reference/                     # Reference materials
│   ├── README.md                     # Reference overview
│   ├── 01-api-reference/             # API documentation
│   │   ├── xrd-api.md
│   │   ├── composition-api.md
│   │   └── function-api.md
│   ├── 02-cli-reference/             # CLI commands
│   │   ├── crossplane-cli.md
│   │   └── kubectl-crossplane.md
│   ├── 03-glossary/                  # Terms & definitions
│   │   └── glossary.md
│   └── 04-cheat-sheets/              # Quick references
│       ├── commands.md
│       ├── patterns.md
│       └── troubleshooting.md
│
├── 10-labs/                          # Hands-on laboratories
│   ├── README.md                     # Labs overview
│   ├── lab-01-installation/          # Lab 1: Setup
│   │   ├── instructions.md
│   │   ├── lab-files/
│   │   └── solutions/
│   ├── lab-02-first-composition/     # Lab 2: Basic composition
│   │   ├── instructions.md
│   │   ├── lab-files/
│   │   └── solutions/
│   ├── lab-03-functions/             # Lab 3: Functions
│   │   ├── instructions.md
│   │   ├── lab-files/
│   │   └── solutions/
│   ├── lab-04-database-platform/     # Lab 4: Database platform
│   │   ├── instructions.md
│   │   ├── lab-files/
│   │   └── solutions/
│   └── lab-05-production/            # Lab 5: Production
│       ├── instructions.md
│       ├── lab-files/
│       └── solutions/
│
├── 11-case-studies/                  # Real-world case studies
│   ├── README.md                     # Case studies overview
│   ├── platform-team-adoption/       # Platform engineering
│   ├── multi-tenant-saas/            # SaaS platforms
│   ├── hybrid-cloud/                 # Hybrid deployments
│   └── edge-computing/               # Edge scenarios
│
├── scripts/                          # Utility scripts
│   ├── install-crossplane.sh
│   ├── setup-providers.sh
│   ├── validate-compositions.sh
│   ├── cleanup.sh
│   └── test-functions.sh
│
├── docs/                             # Additional documentation
│   ├── architecture/                 # Architecture guides
│   │   ├── control-plane-design.md
│   │   └── composition-patterns.md
│   ├── tutorials/                    # Step-by-step tutorials
│   │   ├── getting-started.md
│   │   ├── building-platforms.md
│   │   └── advanced-compositions.md
│   └── videos/                       # Video resources
│       └── video-links.md
│
└── examples/                         # Quick reference examples
    ├── simple-s3-bucket/
    ├── complete-database/
    ├── app-deployment/
    └── multi-resource-composition/

Getting Started

Quick Start (5 minutes)

Install Crossplane:

# Create a Kubernetes cluster (if needed)
kind create cluster --name crossplane-playground

# Install Crossplane using Helm
helm repo add crossplane-stable https://charts.crossplane.io/stable
helm repo update
helm install crossplane \
  --namespace crossplane-system \
  --create-namespace \
  crossplane-stable/crossplane

Verify Installation:
```
kubectl get pods -n crossplane-system
```

Install Crossplane CLI:

curl -sL "https://raw.githubusercontent.com/crossplane/crossplane/main/install.sh" | sh
sudo mv crossplane /usr/local/bin

Run Your First Example:

cd 01-fundamentals/01-installation
./verify-installation.sh

Detailed Setup

See 01-fundamentals/README.md for comprehensive installation and setup instructions.

Learning Path

🌱 Beginner Track (Weeks 1-2)

Goal: Understand Crossplane fundamentals and basic resource management

Fundamentals (01-fundamentals/)
- Install Crossplane
- Understand providers and managed resources
- Learn about Custom Resource Definitions (CRDs)
Basic Compositions (02-compositions/01-xrd-basics/)
- Create your first XRD
- Build simple compositions
- Deploy composite resources

Lab: Complete 10-labs/lab-01-installation/ and lab-02-first-composition/

🌿 Intermediate Track (Weeks 3-4)

Goal: Master composition functions and build reusable platform APIs

Composition Functions (03-composition-functions/)
- Work with Patch & Transform
- Build function pipelines
- Use templating functions (KCL, Go templates)
Real-World Patterns (04-real-world-examples/)
- Database self-service platform
- Application deployment automation
- Network infrastructure management

Lab: Complete 10-labs/lab-03-functions/ and lab-04-database-platform/

🌳 Advanced Track (Weeks 5-6)

Goal: Implement production-ready control planes with security and operations

Security & Compliance (05-security/)
- RBAC and access control
- Secrets management
- Policy enforcement
Operations (06-operations/)
- Monitoring and observability
- Troubleshooting patterns
- Backup and disaster recovery
CI/CD Integration (07-ci-cd-integration/)
- GitOps workflows
- Automated testing
- Deployment pipelines

Lab: Complete 10-labs/lab-05-production/

🚀 Expert Track (Ongoing)

Goal: Extend Crossplane and contribute to the ecosystem

Advanced Topics (08-advanced-topics/)
- Build custom providers
- Develop custom functions
- Implement webhooks
Community Contribution
- Contribute to open-source functions
- Share composition patterns
- Write blog posts and tutorials

Key Concepts

Composite Resource Definition (XRD)

Defines the schema for your custom API:

apiVersion: apiextensions.crossplane.io/v2
kind: CompositeResourceDefinition
metadata:
  name: databases.example.io
spec:
  scope: Namespaced  # New in v2: Namespaced by default
  group: example.io
  names:
    kind: Database
    plural: databases
  versions:
  - name: v1
    served: true
    referenceable: true
    schema:
      openAPIV3Schema:
        type: object
        properties:
          spec:
            type: object
            properties:
              size:
                type: string
                enum: [small, medium, large]
              engine:
                type: string
                enum: [postgres, mysql]

Composition

Templates that define what resources to create:

apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  name: database-aws
spec:
  compositeTypeRef:
    apiVersion: example.io/v1
    kind: Database
  mode: Pipeline  # Use function pipeline
  pipeline:
  - step: patch-and-transform
    functionRef:
      name: crossplane-contrib-function-patch-and-transform
    input:
      apiVersion: pt.fn.crossplane.io/v1beta1
      kind: Resources
      resources:
      - name: rds-instance
        base:
          apiVersion: rds.aws.crossplane.io/v1alpha1
          kind: Instance
          spec:
            forProvider:
              engine: postgres

Composition Functions

Extend composition with custom logic:

apiVersion: pkg.crossplane.io/v1
kind: Function
metadata:
  name: function-patch-and-transform
spec:
  package: xpkg.crossplane.io/crossplane-contrib/function-patch-and-transform:v0.8.2

Popular functions:

function-patch-and-transform: Traditional P&T compositions
function-go-templating: Go template-based composition
function-kcl: KCL language for composition
function-auto-ready: Automatic readiness detection
Custom functions: Written in Go or Python

What's New in Crossplane v2

Namespaced XRs: Composite resources are namespaced by default
No More Claims: Simplified architecture removes the claim abstraction
Better App Support: First-class support for managing applications
Backward Compatible: v1 compositions continue to work

Hands-On Labs

Each lab includes:

Detailed step-by-step instructions
Starter files and templates
Complete solutions
Validation tests

Available Labs

Lab 1: Installation & Setup (30 min)
Lab 2: First Composition (45 min)
Lab 3: Composition Functions (60 min)
Lab 4: Database Platform (90 min)
Lab 5: Production Deployment (120 min)

See 10-labs/README.md for detailed lab instructions.

Best Practices

Composition Design

✅ DO:

Use meaningful, descriptive names for XRDs and compositions
Version your XRDs appropriately
Leverage function pipelines for complex logic
Document composition behavior in annotations
Use namespaced XRs unless you need cluster scope

❌ DON'T:

Embed sensitive data directly in compositions
Create overly complex single compositions
Skip validation schemas in XRDs
Mix v1 and v2 patterns in the same platform

Security

Use RBAC to restrict access to compositions
Leverage external secrets management
Implement policy enforcement with OPA or Kyverno
Enable audit logging
Regularly scan provider images

Operations

Monitor composition reconciliation metrics
Set up alerting for composition failures
Implement backup strategies for XR state
Test compositions with crossplane render
Use GitOps for composition lifecycle

Function Development

Write comprehensive tests for custom functions
Use the official SDKs (Go, Python)
Document function inputs clearly
Handle errors gracefully
Consider performance implications

Resources

Official Documentation

Community

Learning Materials

Tools & Extensions

Providers

Composition Functions

Contributing

Contributions are welcome! This is a learning resource for the community.

How to Contribute

Fork the repository
Create a feature branch (git checkout -b feature/new-example)
Add your example or improvement
Ensure documentation is updated
Submit a pull request

Contribution Guidelines

Follow existing directory structure
Include comprehensive README files
Add comments to complex YAML
Provide working examples
Test all configurations before submitting
Follow Crossplane best practices

What to Contribute

New composition examples
Custom function implementations
Real-world case studies
Improved documentation
Bug fixes and clarifications
Additional labs and tutorials

Roadmap

Planned Content

Advanced multi-cloud patterns
Service mesh integration examples
Cost optimization strategies
Disaster recovery blueprints
Edge computing scenarios
Machine learning platform examples

Stay Updated

Watch this repository for updates as Crossplane evolves. Major updates planned for:

Crossplane v2.2 (February 2026)
Crossplane v2.3 (May 2026)

License

This repository is licensed under the MIT License. See LICENSE for details.

Acknowledgments

Crossplane maintainers and community
CNCF for hosting the project
All contributors to this learning resource
The platform engineering community

Author

Willem van Heemstra

Security Domain Expert & Cloud Engineer
Focus: DevSecOps, Cloud Security, Platform Engineering
Location: Eersel, Netherlands

⭐ If you find this resource helpful, please star the repository!

🤝 Contributions and feedback are always welcome!

📧 Questions? Open an issue or join the Crossplane Slack

Last Updated: December 24, 2025 Crossplane Version: v2.1 (November 2025) CNCF Status: Graduated Project (October 2025)

Name		Name	Last commit message	Last commit date
Latest commit History 19 Commits
01-fundamentals		01-fundamentals
02-compositions		02-compositions
03-composition-functions		03-composition-functions
04-real-world-examples		04-real-world-examples
05-security		05-security
06-operations		06-operations
07-ci-cd-integration		07-ci-cd-integration
08-advanced-topics		08-advanced-topics
09-reference		09-reference
10-labs		10-labs
11-case-studies		11-case-studies
docs		docs
examples		examples
scripts		scripts
LICENSE		LICENSE
README.md		README.md
REFERENCES.md		REFERENCES.md
create-structure.sh		create-structure.sh

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vanHeemstraSystems/learning-crossplane

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Learning Crossplane

📚 Table of Contents

About This Repository

What is Crossplane

Key Features in Crossplane v2.1

Prerequisites

Required Knowledge

Required Tools

Optional Tools

Directory Structure

Getting Started

Quick Start (5 minutes)

Detailed Setup

Learning Path

🌱 Beginner Track (Weeks 1-2)

🌿 Intermediate Track (Weeks 3-4)

🌳 Advanced Track (Weeks 5-6)

🚀 Expert Track (Ongoing)

Key Concepts

Composite Resource Definition (XRD)

Composition

Composition Functions

What's New in Crossplane v2

Hands-On Labs

Available Labs

Best Practices

Composition Design

Security

Operations

Function Development

Resources

Official Documentation

Community

Learning Materials

Tools & Extensions

Providers

Composition Functions

Contributing

How to Contribute

Contribution Guidelines

What to Contribute

Roadmap

Planned Content

Stay Updated

License

Acknowledgments

Author

About

Resources

License

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