In reviewing the Auto-Scaling events for your application you notice that your application is scaling out and in multiple times in the same hour. What design choice could you make to optimize for costs while preserving elasticity?

Answer options:

A.Modify the Auto Scaling policy to use scheduled scaling actions
B.Modify the Auto Scaling Group cool down timers
C.Modify the Amazon Cloudwatch alarm period that triggers your AutoScaling scale down policy.
D.Modify the Auto Scaling group termination policy to terminate the newest instance first.

Answer - B and C
The Auto Scaling cooldown period is a configurable setting for your Auto Scaling group that helps to ensure that Auto Scaling doesn`t launch or terminate additional instances before the previous scaling activity takes effect. After the Auto Scaling group dynamically scales using a simple scaling policy, Auto Scaling waits for the cooldown period to complete before resuming scaling activities. When you manually scale your Auto Scaling group, the default is not to wait for the cooldown period, but you can override the default and honor the cooldown period. Note that if an instance becomes unhealthy, Auto Scaling does not wait for the cooldown period to complete before replacing the unhealthy instance.
For more information on Autoscale cool down timers please visit the URL:
http://docs.aws.amazon.com/autoscaling/latest/userguide/Cooldown.html
You can also modify the Cloudwatch triggers to ensure the thresholds are appropriate for the scale down policy
For more information on Autoscaling user guide please visit the URL:
http://docs.aws.amazon.com/autoscaling/latest/userguide/as-scale-based-on-demand.html