The Public VLAN firewall is too pricy for us. I am in search for a better fit solution.
Which API function do I use to order a shared hardware firewall? Can I order one for a hourly VM?
What happens if I cancel the VM? Is the firewall canceled as well?
Unfortunately, it's not possible to add hardware firewalls for hourly instances ( You can only add Software Firewall), In case that you have a VM (in this case, monthly VM) and you cancel the VM, the hardware firewall will be canceled with it.
Regarding to shared hardware firewall:
Let me know if you need assistance to create an script to share rules between firewalls or if you wish to order a Monthly VM with hardware firewall. I will be glad to help you.