Crossplane is another entry in the class of tools implemented by the Kubernetes Operator pattern but with side effects that extend beyond the Kubernetes cluster. In our last Radar we mentioned Kube-managed cloud services as a technique, and Crossplane does just that. The idea is to leverage the Kubernetes control plane to provision cloud services on which your deployment is dependent, even if they aren't deployed on the cluster itself. Examples include managed database instances, load balancers or access control policies. This tool is noteworthy for two reasons. First, it demonstrates the powerful and flexible execution environment of the underlying Kubernetes control plane. There is no real limit to the range of supported custom resources. Second, Crossplane provides an alternative to the usual options of Terraform, CDK or Pulumi. Crossplane comes with a set of predefined providers for the major cloud services that cover the most commonly provisioned services. It isn't trying to be a general-purpose infrastructure-as-code (IaC) tool but rather a companion to workloads being deployed in Kubernetes. Often associated with the practice of GitOps, Crossplane stands on its own and allows you to stay within the Kubernetes ecosystem when it's necessary to manage external cloud resources. However, Crossplane doesn't help with provisioning Kubernetes itself; you'll need at least one other IaC tool to bootstrap the cluster.
