Setup read operations from slave/secondary mysql system

I have setup the Cluster environment for the read operations from slave/secondary using MySQL and it was working fine and when I create a new site using the bench command, a new database is created on all the master and slave nodes.

But in the Steps to setup readonly environment I have other steps Configurations for read-only replica and Grant access permissions. And If I put those keys in the site_config.json its showing the connection refused error.

If I remove keys form site_config.json its working fine and the data are written in both the master and slave. So please let me know if I need to add those keys for the Cluster environment or its not required.

Note: For the MariaDB Master-Slave environment its working fine if I give the access permissions.

If access permissions are required for Cluster environment could you please provide the example permissions