Hello Sir or Madam
I have experience creating smaller apps like your grocery store shopping app, with a small database backend, and a friendly UI design. I can create such apps with secure and reliable memory storage, which can sometimes be tricky. I would like to support your good idea to provide your customers a comfortable way of shopping at your store. May I ask, what kind of categories are you working with? Are the products that you wish to offer, a subset of a larger catalog of products? Please see my Children's Timer app (in my profile - Portfolio Items), which uses Core Data (Apple's native database framework) to reliably store state information.
Best regards
Joshua