So I have a kubernetes configuration that has two nodes, this in turn creates two load balancer backend services (within GCP).
How can I have session affinity functionality between BOTH backend services?
I thought I would be able to delete the second backend service, and then add the second generated 'backend' to the first backend service - but I'm not sure if this is feasible / possible.
The load balancing is done by the service. So I think you just need a service and behind it some pods (ReplicaSet or Deployment with targeted labels).
About how to make session affinity works, you probably need an ingress with an affinity cookie. In the ingress Kubernetes repository there is an example (here).