Genetous allows you to do your work only through the Frontend without the need to develop a Backend and offers the Backend to you as a service. It uses JSON to communicate with ready services.
Back4App Alternatives
Back4App is described as 'Low code backend to build modern apps. Back4app accelerate backend development, improves development productivity, reduces time to market, and let you scale applications without managing infrastructure' and is a backend as a service in the development category. There are more than 50 alternatives to Back4App for a variety of platforms, including Web-based, Self-Hosted, Windows, Android and iPhone apps. The best Back4App alternative is Supabase, which is both free and Open Source. Other great apps like Back4App are Firebase, bknd.io, Appwrite and Strapi.