Does the data in mongodb provisioned in EC2 gets replicated while Autoscaling?

To deploy a server in Amazon Ec2, I wish to have the mongodb master database in an Ec2 instance itself and at an average I would be having around 5-6 Ec2 instances running in parallel which are scaled by amazon auto-scaling group.

As database is updated frequently and all instances are under Elastic load balancer,it is hard to predict which users data is in which database of Ec2. By following this approach, am i assured of data consistency while scaling in and out ? If it is not the good approach please suggest alternate ways of doing it.