Both SmartScale and R/W splitting cannot be enabled at the same time.
This is because they are two sides of the basic functionality. R/W
splitting and SmartScale both use SQL introspection to determine
whether a query should be directed to a master or a slave. SmartScale
combines this with an intelligent load-balancer. R/W splitting uses a
simpler direct redirection.
In addition to the selection and configuration mechanisms supported, a
routing method should be chosen based on your application abilities:
If the application has full control of the SQL statements submitted
(i.e. not through a third-party tool, or Object-Relational Modeling
library), and can already direct queries to master or slaves based
on the operation type, use Section 6.3.8, “SQL Routing”.