nginx.subdomain.conf

server {
  listen 443;
  server_name example.com;
  location / {
    proxy_pass http://frontend;
  }
  location /api {
    rewrite /api/(.*) /$1 break;
    proxy_pass http://backend;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
  }
}