I am running my server on Google App engine
where i am using nodejs
and i have all other services like mongoDB, Elasticsearch and Redis
de
You can use app engine flexible. https://cloud.google.com/appengine/docs/flexible/
Then set the serivce machines on the same network with the databases.
In such configuration you don't need to set public IPs to the databases so there won't be access to them from outside of the internal network.