Full Stack Developer for scoring Saas Product

In the development stage of a Saas product whose background data is driven off a google spreadsheet. Data is extensive. Need a full stack developer to design/program Saas product, subscription based, based mainly on model outputs (though these are largely embedded in the spreadsheet). Needs to be subscription quality end product. I don't have a strong opinion on platform/programming language, I am not sure what would be the most efficient/best fit, am opened for suggestions.