Crossplane Platform APIs

Build internal platform APIs with Crossplane. Generates Compositions, CompositeResourceDefinitions, Functions (KCL/Python), provider configs for AWS/GCP/Azure, and team-facing claims.

This skill covers Crossplane v1.16+: installing providers (provider-aws, provider-gcp, provider-azure, provider-kubernetes, provider-helm), authoring CompositeResourceDefinitions (XRDs) that define platform APIs (e.g. XPostgresInstance, XCluster), Compositions with composition functions (KCL, Python, Go), claims that developers consume in their namespace, ProviderConfigs for cloud auth via IRSA/Workload Identity, and patterns for building golden-path infra (DB+cache+queue in one claim).

When to use

Use when building internal platforms with Crossplane, defining XRDs and Compositions, writing composition functions, or replacing bespoke Terraform with cluster-native infra.

Examples

Postgres platform API

Self-serve RDS for app teams

Write an XRD and Composition for XPostgresInstance that provisions an AWS RDS Postgres, a security group, a Secret with creds, and a Kubernetes Secret in the claim's namespace — teams just create a tiny PostgresInstance claim

Composition function in KCL

Branch on env: prod vs dev

Convert my patch-and-transform Composition into a function-based Composition using crossplane-contrib/function-kcl that picks db instance class and Multi-AZ based on the claim's spec.parameters.environment