I gave Vertx a chance a few years back and while it worked, it's not great for building services on, unless your needs are extreme scale. And in the latter case

I gave Vertx a chance a few years back and while it worked, it's not great for building services on, unless your needs are extreme scale. And in the latter case, you might be better off with a language like Go. It's very async/reactive and a bit of magic hides behind those nice builder patterns. My advice: If you are just building a regular service that doesn't need to scale (and 90% of apps do not need Twitter scale), just stick with sync.