Your 'cloud code' is just another microservice. You write it in whatever language you wish, package it with its dependencies as a docker image which will then be deployed onto hasura's platform and linked with the rest of your app's infrastructure.

Essentially, you don't have to deploy anything on your own server. Whatever functionality hasura's 'batteries' can't provide (yet), you write it as another microservice. At the end of the day, your app is composed of several microservices (containers running in the cloud), few hasura provided and few custom written.