You have an instance group that you want to load balance.

[Reference: https://cloud.google.com/load-balancing/docs/https/, According to this guide for setting up an HTTP (S) load balancer in GCP: The client SSL session terminates at the load balancer. Sessions between the load balancer and the instance can either be HTTPS (recommended) or HTTP., https://cloud.google.com/load-balancing/docs/ssl, , , , ]