GCP - should I have multiple egress IP address?

Solution 1:

This depends on your cloud implementation, even when you have 65535 available ports for each IP address, GCP Cloud NAT will only use 64512 for each protocol, so if your implementation on GCP requires more than those number of ports, then you must add new static IPs, this is automatically solved when using "Auto-Allocation" to scale up or down at any given moment without manual intervention, but this would select any random IP address to use (which might not be white-listed).

I am wild guessing here (since I don't know much about your implementation), but I would use multiple static IPs in order to have some spare ports in case your system out-grow those limits.