Since all Frontend code is written in JavaScript, it makes sense to have the server code written in JavaScript as well as we do quite a bit of work on the server. Also, we do serve isomorphic views so Node is a big help in that regards.

Java even with webjars, hot reloading (jrebel), and what not just can't keep up with the superior Node tooling not to mention more and more frontend developers know node and not Java.

I still prefer Java/JVM languages though for backend work.

Because using Java for a front end server is a horribly inefficient and painful experience.

Freedom and Responsibility! Teams are free to choose the tools that work for them. Netflix technical direction operates more like an ecosystem than a hierarchy.

I'm guessing it's their use of React both on the front-end and back-end.