[Spivak]

You need it to jump around because your RDS database might fail over to a different AZ.

Being able to move workloads around is kinda the point. The need exists irrespective of what you use to deploy your app.

[toredash]

The nice thing about this solution, its not limited to RDS. I used RDS as an example as many are familiar with it and are known to the fact that it will change AZ during maintenance events.

Any hostname for a service in AWS that can relocate to another AZ (for whatever reason), can use this.