If a client in us-east1-b calls a service in us-east1-b over public IP, what is the result?

When a client in us-east1-b accesses a service in the same region (us-east1-b) over public IP, an egress charge is incurred. This is because the request utilizes Google's public internet infrastructure, and even though both the client and the service are in the same region, transiting data over public IPs typically results in egress charges.

In a typical configuration, Google Cloud charges for egress traffic that goes outside the network boundaries, regardless of whether the source and destination are in the same region when using public IPs. Thus, any outbound data from the Google Cloud resources incurs charges.

Using VPC peering is a way to avoid these charges since it allows private communication between resources within distinct VPC networks without using public IPs. However, this scenario specifically describes using public IPs, so VPC peering would not apply, nor would it impact the charges incurred when utilizing public IP addresses.

In summary, when services communicate over public IPs, even within the same region, it leads to egress charges, which underscores the importance of understanding the differences between using public and private IP connections in Google Cloud architecture.