What is the maximum total number of VM instances allowed per peering group?

The maximum total number of VM instances allowed per peering group is indeed 15,000. This limit is vital for ensuring optimal performance and managing resources effectively within Google Cloud's networking environment. Peering groups are utilized to connect different Virtual Private Clouds (VPCs), allowing for networking benefits such as reduced latency and improved data transfer capabilities between them.

Having a cap on the number of VM instances helps maintain a balance between resource availability and performance. If the number exceeded 15,000, it could lead to complications such as increased management overhead, potential performance degradation, and complexities in network routing. Understanding this limit is essential for network engineers, as it affects how they design and scale their cloud infrastructure effectively.