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 18.104.22.168 or 22.214.171.124
Europe 126.96.36.199 or 188.8.131.52
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).