title: Will AWS transfer data between availability zones if I request data from RDS?
body: <p>I have a Multi-AZ ECS cluster with EC2 instances and an Aurora RDS cluster with cross-az read replicas. I use the cluster URL for selecting data in RDS.
  Does the cluster automatically forward my request to the RDS in the same AZ, if it is possible? If not, how can I prevent unnecessary data transfer between availability zones? (I want to use RDS in different AZ, if and only if the RDS in the same AZ is out of service)</p>
  
  <p>According to AWS documentation:</p>
  
  <p>"Data transferred between Amazon RDS and Amazon EC2 Instances in the same Availability Zone is free."</p>
  
  <p>"Amazon RDS DB Instances inside VPC: For data transferred between an Amazon EC2 instance and Amazon RDS DB Instance in different Availability Zones of the same Region, Amazon EC2 Regional Data Transfer charges apply on both sides of transfer."</p>