EDGE SSO communication with Postgres Master ?

Google Cloud Apigee
1

Per https://docs.apigee.com/private-cloud/v4.19.06/installing-edge-sso-high-availability

indicates following

Both instances of Edge SSO must be connected to the same Postgres server. Apigee recommends using a dedicated Postgres server for Edge SSO and not use the same Postgres server that you installed with Edge.

Whats the purpose of Edge SSO communication to Postgres Master ?

Understand that Edge SSO communicates to OpenLDAP for User Management information, but reason for EDGEE SSO with Postgres Master is not clear in the documentation

2

When you install the sso, it creates a table for sso in Postgres. The table contains the token and user-related information. You cannot directly write to the standby Postgres, it always writes to the Postgres master.