SYSTEM Cited by 1 source
Crossplane¶
Crossplane is a CNCF project that turns Kubernetes into a universal control plane for provisioning cloud resources — databases, buckets, VPCs, SaaS accounts, anything with an API — across one or more clouds. Every external resource is modeled as a Kubernetes custom resource (CR), reconciled by a provider controller that calls the target cloud's API and continuously drives observed state toward declared state.
This is a structurally different primitive from Terraform's plan-and-apply model:
| Axis | Terraform | Crossplane |
|---|---|---|
| State storage | Explicit state file | Kubernetes API (etcd) |
| Reconciliation | Run-triggered | Continuous controller loop |
| Drift correction | Manual re-apply | Automatic via controller |
| API surface | HCL + CLI | K8s CRDs + kubectl / API |
| Composability | Modules | Composite Resource Definitions + Compositions |
| RBAC | Cloud IAM | Kubernetes RBAC |
Crossplane slots cleanly into the same Kubernetes-native GitOps stack (ArgoCD / concepts/gitops) that delivers application workloads — one reconciliation substrate for both infrastructure and apps is the load-bearing design choice.
Composite Resources (XRDs + Compositions)¶
Crossplane's Composite Resource Definitions
+ Compositions
are how platform teams package N cloud primitives behind one
high-level CRD — a database stack XRD might instantiate an RDS
instance + IAM role + Secrets Manager entry + VPC security group +
CloudWatch alarm in one kubectl apply. Documented as the
patterns/crossplane-composition pattern in the wiki.
Seen in¶
- sources/2026-02-26-aws-santander-catalyst-platform-engineering — Santander Catalyst uses Crossplane "as a universal resource provisioner" at the core of the EKS control plane cluster: "Crossplane plays a fundamental role, acting as a universal resource provisioner that Santander uses to manage resources across multiple cloud providers consistently and declaratively." The platform's stacks catalog is "a library of composite resource definitions and Compositions enabling quick and standardized creation of complex environments" — the unit of reuse behind Catalyst's headline provisioning-time collapse (90 days → hours / minutes).
Stub page — Crossplane internals (providers, Composition Functions, managed resources vs composite resources, packaging) out of scope until a future source drills into them.
Related¶
- concepts/universal-resource-provisioning — the abstraction Crossplane realizes
- patterns/crossplane-composition — the XRDs + Compositions pattern
- systems/terraform — the plan-and-apply IaC alternative
- systems/argocd — the GitOps counterpart that delivers applications against the same K8s API surface
- systems/kubernetes — the control-plane substrate Crossplane repurposes for infrastructure