crossplane

name	crossplane
description	Use when managing cloud infrastructure through Kubernetes with Crossplane. Covers providers, managed resources, compositions, XRDs, claims, and the control plane pattern. USE FOR: Kubernetes-native cloud provisioning, Crossplane compositions, XRDs and claims, control plane pattern DO NOT USE FOR: standalone CLI-driven IaC (use terraform or pulumi), Kubernetes application deployment (use kubernetes or helm)
license	MIT
metadata	{"displayName":"Crossplane","author":"Tyler-R-Kendrick"}
compatibility	claude, copilot, cursor
references	[{"title":"Crossplane Documentation","url":"https://docs.crossplane.io"},{"title":"Crossplane GitHub Repository","url":"https://github.com/crossplane/crossplane"}]

Crossplane

Overview

Crossplane is an open-source Kubernetes add-on that extends the Kubernetes API to provision and manage cloud infrastructure. Instead of using separate IaC tools, you define cloud resources as Kubernetes custom resources and manage them with kubectl, GitOps, and the Kubernetes reconciliation loop.

Core Concepts

Providers

Install cloud providers to manage external resources:

apiVersion: pkg.crossplane.io/v1
kind: Provider
metadata:
  name: provider-aws
spec:
  package: xpkg.upbound.io/upbound/provider-aws-s3:v1.7.0

Managed Resources

Cloud resources represented as Kubernetes objects:

apiVersion: s3.aws.upbound.io/v1beta2
kind: Bucket
metadata:
  name: my-app-assets
spec:
  forProvider:
    region: us-east-1
    tags:
      Environment: prod
  providerConfigRef:
    name: aws-config

Composite Resources (XRDs + Compositions)

Define custom APIs that abstract cloud details:

CompositeResourceDefinition (XRD)

apiVersion: apiextensions.crossplane.io/v1
kind: CompositeResourceDefinition
metadata:
  name: xdatabases.platform.example.com
spec:
  group: platform.example.com
  names:
    kind: XDatabase
    plural: xdatabases
  claimNames:
    kind: Database
    plural: databases
  versions:
    - name: v1alpha1
      served: true
      referenceable: true
      schema:
        openAPIV3Schema:
          type: object
          properties:
            spec:
              type: object
              properties:
                engine:
                  type: string
                  enum: [postgres, mysql]
                size:
                  type: string
                  enum: [small, medium, large]
              required: [engine, size]

Composition

apiVersion: apiextensions.crossplane.io/v1
kind: Composition
metadata:
  name: xdatabases.aws.platform.example.com
spec:
  compositeTypeRef:
    apiVersion: platform.example.com/v1alpha1
    kind: XDatabase
  resources:
    - name: rds-instance
      base:
        apiVersion: rds.aws.upbound.io/v1beta2
        kind: Instance
        spec:
          forProvider:
            engine: postgres
            instanceClass: db.t3.micro
            allocatedStorage: 20
      patches:
        - fromFieldPath: spec.engine
          toFieldPath: spec.forProvider.engine
        - type: FromCompositeFieldPath
          fromFieldPath: spec.size
          toFieldPath: spec.forProvider.instanceClass
          transforms:
            - type: map
              map:
                small: db.t3.micro
                medium: 
                 

Claims

Application teams request infrastructure using the custom API:

apiVersion: platform.example.com/v1alpha1
kind: Database
metadata:
  name: orders-db
  namespace: orders
spec:
  engine: postgres
  size: medium

Installation

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

Best Practices

• Use Compositions + Claims to create platform APIs that abstract cloud-specific details from application teams.
• Use GitOps (Argo CD, Flux) to manage Crossplane resources declaratively.
• Pin provider versions for reproducible infrastructure.
• Use providerConfigRef to separate credentials per environment.
• Use patches and transforms in Compositions to map simple claim inputs to complex cloud configurations.
• Monitor resource health with kubectl get managed — Crossplane continuously reconciles desired vs actual state.