this is nginx / openresty config - upstream is just definition of server / bunch of servers if you do loadbalancing or want to configure stuff you can do

stream {
  upstream something {
     server xxx:123;
     server yyy:321;
  }
  server {
     listen 666;
     proxy_pass something;
  }
}

docs.nginx.com/nginx/…/tcp-udp-load-balancer/

I use openresty with autossl, it renews certificates automatically. The only problem is maintaining subdomain allowance otherwise bots will ddos letsencrypt that would soft ban you to create certificates for new domains / subdomains.