Well, that’s a lot of questions.
It’s usually a very bad idea to share mutable state in an concurrent application. If you need to share data, you can use `Shared Data`
Vert.x Core Manual - Vert.x
Eclipse Vert.x is a tool-kit for building reactive applications on the JVM.
For routing, you usually don’t need more that one verticle doing the job. But yeah, you can also create more than one, and they’ll be triggered in a round robin manner.