The data store of Telerik Backend Services is actually not relational but document based (NoSQL). This means there is no need to define tables like in a relational database. However, for easier usage, cleaner API and best performance we have introduced the concept of Content Types. Similarly to a relational table, the content type defines a common structure for the items you will store together in the database, but it does not necessarily enforce that all items have the same fields.
For your application you would need to create content types like Customer, ServiceProvider and ServiceRequest. You can also define relations between them by using fields of type Relation. For more details about our Cloud Data service, please have a look at the following sections in our documentation:
Storing Data in the Cloud
Introduction to Data Storage in Telerik Backend Services
Of course, you are welcome to send us any questions that may arise during your startup with Backend Services.