Now come across a problem, though. Our code resides in the Main.kt file, which grows bigger and bigger. We can start splitting it by using verticles.

You can think of a verticle as a lightweight actor.  Let's see an example; look at the following code:

class ServerVerticle: CoroutineVerticle() {

    override suspend fun start() {
        val router = router()
        vertx.createHttpServer().requestHandler(router::accept).listen(8080)
    }

    private fun router(): Router {
        val router = Router.router(vertx)
        // Our router code comes here now
        ...
        return router
    }
}

Now we need to start this verticle. There are different ways of doing that, but the simplest way is to pass the instance of this class to the deployVerticle() method:

vertx.deployVerticle(ServerVerticle())

Now our code is split into two files, ServerVerticle.kt and Main.kt.

Notice, though, how /api/v1/cats/ is repeated every time. Isn't there a way to remove that redundancy? Actually, there is. And it's called subrouter.