DualConnection consistency is controlled by com.atlassian.db.replica.spi.ReplicaConsistency.
Currently, there's no default consistency implementation. Consistency model highly depends on the database and application's needs. There's one example of the implementation for Postgres available in the integration test.
The easiest way to start is to use PessimisticPropagationConsistency.
Every write operation is registered by ReplicaConsistency#write method.
DualConnection verifies
the state of replica's consistency by calling ReplicaConsistency#isConsistent method.