All users update 1 single firebase document?

Hey, I've created an app where users can order services. I built an admin panel using Firebase, which shares the app's database. To track orders and revenue, I planned to use a single collection that updates with each purchase: incrementing orderCount by 1 and totalIncome by the purchase amount. This data should display in the admin panel.

However, I encountered two issues:

1. I'm unsure how to reference this specific collection every time a user makes a purchase in FlutterFlow.

2. I'm concerned about performance if multiple users make purchases simultaneously, potentially overwhelming the single Firebase document.

Is there a better approach? If not, how can I correctly reference this specific Firebase collection on the checkout page for all users?

Thanks a lot for your help!