Best Java Stack For a Modern Web App

What’s the best software stack for a modern web application on the Java platform? I am building the backend in Spring Boot persisting in a MySQL database. Keeping it simple.

Candidate for the front-end is React.js, but I have no experience in it. Any suggestions how to start up rapidly with an easy to use API?

Since Spring Boot 2 has been released lately, how can migrating be of help? Pivotal’s introductory webinar focused largely on it’s reactive, non-blocking functionality. This is probably a performance enhancing model for high through-put sites, but will not boost my productivity in the short term nor be of value for a platform with little traffic.