MySQL Replication Master Slave Architecture - Web app that is based on the SLAVE DB

We are developing a web application (Spring mvc based app) that uses a MySQL DB. (lets call it the "original app") The DB architecture uses a MASTER-SLAVE configuration with replication. The web app uses the MASTER for the functionality.

We are now developing a Back-office application for our "original app". This back office is in itself a web app (spring mvc based).

In order to reduce the performance impact on the "original app" we would like to use the SLAVE replica as the DB for the back-office.

This replica DB will include unique tables (that will exists only on the SLAVE, to serve the back-office app).

Non of us ever worked in such architecture, and we are pretty intimidated by this, therefore we have some questions:

1) Is this architecture even viable? 2) In case of a replication-error , How hard will it be to recover? remember, that the SLAVE will consist of tables that are not in the MASTER 3) Any other tips \ information we can use?

Cheers!