Short.io serves the application via the IP addresses, which you need to apply while domain configuration.
1. We have 4 IPs:
America, Asia and Africa 184.108.40.206 or 220.127.116.11
Europe 18.104.22.168 or 22.214.171.124
2. You can use cloudflare.com. In this case, you will use dynamic pool of IP addresses.
3. We can create another IP for you (as for our Enterprise customer).