Cloud Load Balancing supports proxying traffic to external backends outside Google Cloud. To define an external backend for a load balancer, you use a resource called an internet network endpoint group (NEG).

You can use this type of deployment when you want to serve content from an external backend, but you want your Google Cloud load balancer to be the frontend. This lets you do the following:

• Use Google Edge infrastructure for terminating your user connections.
• Direct the connections to your external backend.
• Deliver traffic to your public endpoint across Google’s private backbone, which improves reliability and can decrease latency between client and server.
• With global load balancers, you can use Cloud CDN to cache content for your external backend

Internet NEGs primarily route traffic to external endpoints. Unlike backend services connected to Compute Engine or other internal services, Internet NEGs do not provide inherent capabilities to modify request or response headers (e.g., removing or adding headers).