Early in the project you should determine if you will use the SDK or not. Keep in mind, if you are using the Adaptation tools to add custom fields, if those fields require business logic, the SDK is required. For example, if you add a field called "bonus plan" and you need to calculate the field value, or base the field value based on a comparison of other fields, then you need the SDK.
When you need the SDK, the recommended landscape is described below. As mentioned in the previous blogs, an additional tenant is needed. For SDK, you need a tenant designated as the Development tenant. Only development work is done on this tenant.
One of the test tenants is designated TEST, the other DEV. In the TEST tenant you do the main configuration and all testing. From this tenant the development tenant is created. The DEV tenant is done by requested a solution profile with full copy. The DEV tenant has only developers an only has basic scoping and whatever is required for the development. Unit tests are performed in the DEV tenant. The solution is then deployed to TEST where it is scoped and tested. This is an iterative process until the solution is accepted and is ready to move to production. Once deployed to production, the SDK solution is scoped, configured, with cut over to production.
The next blog goes into the details of the deployment process with the SDK.