I'd like to provide users with "just another shopping app" for brick-mortar-commerce.

Based on existing/reused shopping lists and experiences of all (anon) users the app shall make suggestions to individual users for new items and for sorting of items in the list for efficient filling of the basket/shopping cart

Hence data shall be edited on the app, stored and retrieved by REST calls and analysed on the server. ML models shall be generated from all users (anonymously) and provided back to the app.

Ideally the app would allow to use "Sign in with apple" Which backend would be ideal for this? Shall I go and learn for Vapor and/or Kitura (or forget about an own backend and go for icloud)?

Thx in Advance - C