My basic nginx configuration for a node.js express application.

gistfile1.txt

upstream api {
        server  127.0.0.1:3000;
        keepalive 10;
}
server {
    listen 80;
    server_name yourdomain.com www.yourdomain.com;

#
#   You can ignore the majority of these next lines,
#   they're for if your app will be behing cloudflare.
#
#    set_real_ip_from 204.93.240.0/24;
#    set_real_ip_from 204.93.177.0/24;
#    set_real_ip_from 199.27.128.0/21;
#    set_real_ip_from 173.245.48.0/20;
#    set_real_ip_from 103.22.200.0/22;
#    set_real_ip_from 141.101.64.0/18;
#    set_real_ip_from 108.162.192.0/18;
#    set_real_ip_from 190.93.240.0/20;
#    set_real_ip_from 2400:cb00::/32;
#    set_real_ip_from 2606:4700::/32;
#    set_real_ip_from 2803:f800::/32;
#    real_ip_header CF-Connecting-IP;
#    proxy_set_header  X-Real-IP  $remote_addr;
#    proxy_set_header  Host       $host;
#    proxy_set_header  X-Forwarded-For $proxy_add_x_forwarded_for;

    location / {
        # Proxy all requests to your API.
        proxy_pass http://api;
    }

    location ~* /.+\.(jpg|png|gif|jpeg|css|js|mp3|wav|swf|mov|ico)$ {
      # Document root for the static files.
      root /home/api/public;
      expires 864000;
    }

    location = /50x.html {
      #  When your app is unreachable, this file will be used
      root   /var/www/nginx-default;
    }
 }

Thanks @ndrut it works well for my use case