Firestore and Android Best Practices

[perissf1]

Hi,
first I am a novice in Android development, and I want to thank you for sharing the method DocumentReference#dataObjects for creating Flows as results of Firestore queries. This should definitely appear in the Firestore guides, but apparently it's still not there.
Second, after reading your blog article Adding complex queries to a Jetpack Compose app, I see that the queries appearing there are really basic, I am not sure they are enough for learning how to do a real app. For example, I am dealing with a catalogue of products grouped by categories, to list in a shop, and I am struggling how to represent them in the model and the UI using Flows. Suppose that in the back end I want to display the list of categories, each with the number of products belonging to it. What model would you use to store the data, and how to retrieve them using Flows? Thanks!