Google Professional Cloud Architect: Shared VPC Architecture Patterns

Shared VPC is an organizational architecture as much as a networking feature. It lets resources in service projects use subnets from a VPC network that lives in a host project, which means network control can be centralized while application teams retain their own project boundaries.

That separation is useful in enterprises where networking, security, billing, and application delivery are owned by different groups. It is also easy to misuse if the organization treats the host project as a giant shared subnet pool without an operating model.