Most platform teams start with a single cluster doing everything. Control logic, workloads, CI pipelines, observability, all running together. It is the pragmatic starting point and there is nothing wrong with it.

But it creates a hidden coupling problem. When your build pipeline hammers the cluster during a big release, your production workloads feel it. When you want to scale observability independently, you can’t without touching everything else. When a compliance requirement asks you to isolate certain workloads, you are refactoring the entire platform.

The lesson: planes are how you escape that coupling