@tonyz80 hi, I am building an app with similar requirements. I would like to know your recommendations. I have checked PrestoAPI with MongoDB (https://youtu.be/6C45qCt41VY) as @jared recommended and it looks like a feasible solution.
I was planning to use mainly Firebase as an initial solution (which will be changed later) for data storage (orders) and especially because of the listener function that is supported with Firebase. Nevertheless, I was planning to sync data with google sheet to allow the integration with other systems that are easily designed with google sheet (ex. Another Thunkable app or AppSheet, … for HR and Customer Support).
Would be happy to arrange a meeting if possible. But in all cases would appreciate your recommendations.