Currently we have an application on Google App Engine using Cloud SQL for our database. I am trying to find alternatives to increasing the database tier to handle increased load on our database, and believe that adding read replica's will help with these increased loads.

My issue is that it is not exactly clear if there is anything necessary for us to do once the read replica is set up to use it. Our application is running on App Engine standard environment, running PHP and using MySQLi to connect to the Cloud SQL instance.

Googling for this issue has come up with a small number of similar questions specific to Cloud SQL on SO, all of which do not have any answers, and more generic advice talks about setting up load balancing or application-level read/write balancing.

Once I have created my Google Cloud SQL read replica, do I need to do anything on either the Cloud SQL end or the App Engine end to start using the read replica?