How to answer from different servers for one domain?

Question

Nginx

Site.com is located on a server with 1.1.1.1
How, where and what to configure so that specific site.com/files/* addresses are opened from server 2.2.2.2?
The files.site.com variant is not suitable, because the simplest SSL was bought.

Answer 1

upstream files_backend {
    server 2.2.2.2;
}

server {
    location /files/ {
        proxy_pass http://files_backend;
    }
}

Answer 2

Install on 1.1.1.1 nginx. And on 2.2.2.2 and 3.3.3.3 apache (or whatever you want). Put the certificate itself to nginx, and register two servers, 2.2.2.2 and 3.3.3.3, with two uplinks.
How, whom and why to steer should be read to the nginx doc. You can't tell this in one post.
Yes. And from nginx to apache, you can send requests over regular http.

Answer 3

Regarding files.site.com - just take a separate certificate, from the same StartSSL or Lets Encrypt.