I’ve been using Vertx for a while now, and so far it hasn’t disappointed me. There’s one thing though, because Vertx came out before Java 8, it doesn’t use java.util.concurrent.CompletableFuture. Instead, it rolls its own future/promise implementation called io.vertx.core.Future. There was a thread on the Vertx discussion group a few days ago, I wrote about what I knew. Here’s a copy. I’ve noticed that CompletableFuture sometimes assigns my HttpClient instance to run on another thread, which leads to a Vertx warning.