Create one Pub/Sub topic. Create one pull subscription to allow the audit services to share the messages.

Create one Pub/Sub topic. Create one pull subscription per audit service instance to allow the services to share the messages.

Create one Pub/Sub topic. Create one push subscription with the endpoint pointing to a load balancer in front of the audit services.

Create one Pub/Sub topic per authentication service. Create one pull subscription per topic to be used by one audit service.

Create one Pub/Sub topic per authentication service. Create one push subscription per topic, with the endpoint pointing to one audit service.