From https://github.com/sassoftware/viya4-iac-k8s/blob/main/docs/CONFIG-VARS.md :
PostgreSQL Servers
When setting up external database servers, you must provide information about those servers in the postgres_servers variable block. Each entry in the variable block represents a single database server.
This code only configures database servers. No databases are created during the infrastructure setup.
However, the task "https://raw.githubusercontent.com/sassoftware/viya4-iac-k8s/main/roles/kubernetes/database/postgres/create_databases/tasks/main.yaml" creates the SharedServices DB when the postgres_server_name is "default".