So, you have a server side Java application and you need to be able to authenticate your users without the hassle? Then App ID is for you. There's no easier way to create a scalable app than to use the nimble IBM WebSphere Liberty application server in a Docker image and run it with IBM Cloud Container Service.
Vaadin Bakery App Starter is a proven full-stack reference application you can use as a starting point for many serious business web apps. It contains many commonly needed features, like RDBMS database accessed using solid JPA+EJB (or Spring) -based persistency and business layer, mindful authentication and authorization, and a UI code structure suitable for non-trivial, large-scale business applications.