Separating business logic and Nodejs api for Angular Node JS project

I am crating a project with has the below components.

1. Angular 7
2. Node Js
3. MongoDB

The Angular and the Node JS API is hosted on the same server because the Angular need to access API for action (it can be on different as well but both are internet facing).
The Node JS connects to MongoDB for database realated stuff.

The challenge is that we don't want to expose the Business Logic on internet due to security reasons and best practice.
Is that any way I can write any wrapper over NodeJs and host it over the internet and the original API (created in NodeJS) containing the business logic on non internet zone.
Any reference or link will be appreciated.

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