Ask HN: How Flutter copes with complex business logic when paired with Firebase?

My company recently decided to go with Flutter and Firebase for building a mobile app. I have no experience with either. Now, my concern is that we could pretty soon start dealing with a huge amount of data and Flutter would be the only way to process it. Are there any experiences with this kind of situation? Is Flutter coping well with doing the "select" part over few joined tables? I believe if the app starts gaining traction that a proper backend should be built, but what is the limit of the Flutter and Firebase alone?