How Google Load balancer routes Requests to backends, in Google Cloud?

GLB can load balance to Instances running in multi-regions

Single GLB for multiple Instance Groups (running in Multi-Regions)

All Instance Groups in Single VPC (Global)

Single global IP address -> GLB

Simple DNS setup for Single GLB IP

GLB sends request to first layer of Google Front Ends (GFE)

GLB selects an GFE instance, located closest to Clients anywhere in the world

GFE receives requests and relays them to a second tier of GFE

GFE second tier constitutes a global network of Servers spread across Globe

GFE second tier sends Requests to corresponding backends, regardless of the regions they are located in