How to change backend technology iteratively?

Background

Our backend is currently written in Grails. We would like to change the backend to NodeJs. We would like to execute the change in small iterations. We deploy everything on AWS.

Question

How to change the technology from Grails to NodeJs iteratively?

My opinion

Although we don't use Microservice Architecture (and none of us has any experience with it) I personally would:

1. build a NodeJs server before our Grails server (something like a Gateway API maybe?)
2. at first the NodeJs would just pass requests/responses to/from Grails
3. then we would move other functionality from Grails (request logging, validations, ...) until we moved everything needed. (Maybe we keep something on Grails but most of the logic should end up on NodeJs.)