The recommendations for the vRealize Appliance have changed with 6.2, the published reference architecture now does not recommend using an external Postgres database (either vPostgres appliance, a 3rd party Postgres deployment or using a third vRealize Appliance as a stand-alone database installation). Instead the recommended layout is shown in the diagram below. One instance of postgres on the primary node becomes an active instance, replicating to the second node which is passive. In front of these a load balancer or DNS entry points to the active node only. Fail-over is still a manual task, but it does provide better protection than a single instance.
The cafe portal and APIs are still load balanced in an active/active configuration and are clustered together.