Hey ed, this is Ram, the author of the post. In the context of Infrastructure SaaS, a data plane is the system that is the infrastructure that you provide as service. For example, let us say you are building a company that provides Postgres as a service. In this case, Postgres is your data plane. Typically, your users will want the Postgres to be deployed in a specific region or cloud provider.They would run queries against the Postgres cluster.

Control plane is the central lifecycle management system that helps provide all the SaaS experience for your Infra SaaS application, manages the metadata for your application and also pushes this information to all the data planes. Example of lifecycle management operations could be creating an user, a new organization, provisioning your data plane in a specific region, deleting a cluster etc.

The data plane is your product that you want to sell to your customers and control plane is the central system that helps you to make your product work in a self serve way with your customers.

This example can also be mapped to internal use cases. Many companies manage their own infrastructure internally and end up having to build a central control plane to manage all the different infrastructure that they provide as a service to their developers. Hope this helps.