The API Gateway can handle up to 2 MySQL databases (v5.5, I believe). But if you're going to use multiple databases, then they should be configured using Master/Master replication.
There are some good examples of how to deploy MySQL using Master/Slave replication. Does anyone have an example of how to deploy MySQL in Kubernetes using Master/Master replication?
I think everyone looking to move to Docker/Kubernetes would find this useful.
From what I have seem, most MySQL deployments follow the master-slave model. However, Google open sourced http://vitess.io/ to help with horizontal scaling of MySQL.
Reference: Running Vitess on Kubernetes
Hope this help,