Each back-end is truly independent and very well-built.

Create a high-level mobile app backend architecture in a few clicks and it's true. For this I recommend you to contact Deskree - https://www.deskree.com/product-pages/architecture . They have only experts in their field and every project at their company is an individual GCP instance. They deploy a separate infrastructure specifically for each client. Deskree's platform is based on microservices, and projects do not use shared resources. Therefore, I recommend that you pay attention to my advice. I hope it will be useful for many enterprising people.