Do I need a domain+certificate to request a backend on another server?

Question

Digital certificates

Good afternoon.
There is a react application with server rendering on the site.com domain of server 1. It already has https and ssl configured.
When a user opens the site.com page, requests go to the backend located on server 2.

Do I understand correctly that for the requests to work correctly, it is necessary to create a domain for the back (server 2) and sign a certificate?
Are there any other options to set up https interaction with the backend (server 2)?

Answer 1

Are there any other options to set up https interaction with the backend (server 2)?

Raise a location inside your domain, which will be a reverse proxy to the 2nd service.

Answer 2

Necessary. Requests from https origin to http origin should be blocked by browser policy