i didnt think that thru..... yes it is possible for only part of a stack to be sold.
and yes thats a really good idea to add a name to each entry
omg theres so many factors to this. i may be in over my head.
Your biggest factor here is the quality of the app users' Internet connectivity.
Only you can answer that question for us.
Regarding the complexity of online inventory management, there are some YouTube videos that show how to do inventory management on shared Google Sheets. I like Google Sheets as a shared data base because their contents are plainly visible to their owner in a browser.
https://www.google.com/search?q=youtube+google+sheets+inventory+management
Coincidentally, the test server ai2-test.appinventor.mit.edu has a Google Sheets component that's fairly simple to use, after some well documented administrative setup work with Google
http://ai2-test.appinventor.mit.edu/reference/components/storage.html#Spreadsheet
Alternative ways of getting at your Google Sheets can be found at
if you are worried about that component never getting into production.