After install the sandbox from the Hortonworks, you can visit the http://localhost:50070 page to find the information about the HDFS cluster. YARN job manager can be access via http://localhost:8088.

Java Futures are the way to support asynchronuous operations. Learn the basics of Java 9 Parallelism before read this post.

The CompletableFuture has been introduced since JDK 8 (2014). This is a abstraction over the `java.util.concurrent. Learn the basics of Java 9 Parallelism before read this post.

Spring property and profile manangement is explained.

This is a short explanation of how to use Spring boot CLI to create project and run in the macOS.