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 22.214.171.124 or 126.96.36.199
Europe 188.8.131.52 or 184.108.40.206
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).