Step 2: Specify the Scaling Strategy - AWS Auto Scaling

Step 2: Specify the Scaling Strategy

Use the following procedure to specify scaling strategies for the resources that were found in the previous step.

For each type of resource, AWS Auto Scaling chooses the metric that is most commonly used for determining how much of the resource is in use at any given time. You choose the most appropriate scaling strategy to optimize performance of your application based on this metric. When you enable the dynamic scaling feature and the predictive scaling feature, the scaling strategy is shared between them. For more information, see How Scaling Plans Work.

The following scaling strategies are available:

  • Optimize for availability—AWS Auto Scaling scales the resource out and in automatically to maintain resource utilization at 40 percent. This option is useful when your application has urgent and sometimes unpredictable scaling needs.

  • Balance availability and cost—AWS Auto Scaling scales the resource out and in automatically to maintain resource utilization at 50 percent. This option helps you maintain high availability while also reducing costs.

  • Optimize for cost—AWS Auto Scaling scales the resource out and in automatically to maintain resource utilization at 70 percent. This option is useful for lowering costs if your application can handle having reduced buffer capacity when there are unexpected changes in demand.

For example, the scaling plan configures your Auto Scaling group to add or remove Amazon EC2 instances based on how much of the CPU is used on average for all instances in the group. You choose whether to optimize utilization for availability, cost, or a combination of the two by changing the scaling strategy.

Alternatively, you can configure a custom strategy if an off-the-shelf strategy doesn't meet your needs. With a custom strategy, you can change the target utilization value, choose a different metric, or both.


For the beginner tutorial, complete only the first step of the following procedure and then choose Next to continue. (You can skip the rest of the procedure because the tutorial focuses on using the default scaling strategy, Optimize for availability, that keeps the average CPU utilization of your Auto Scaling group at 40 percent.)

To specify scaling strategies

  1. On the Specify scaling strategy page, for Scaling plan details, Name, enter a name for your scaling plan. The name of your scaling plan must be unique within your set of scaling plans for the AWS Region, can have a maximum of 128 characters, and must not contain pipes "|", forward slashes "/", or colons ":".

  2. For each type of resource, provide the following scaling instructions.

    1. For the Scaling strategy, choose one of these options: Optimize for availability, Balance availability and cost, Optimize for cost, or Custom.

    2. If you chose Custom in the previous step, choose your custom settings under Configuration details. Here you can find the list of metrics available to you (if any) and related graphs based on data from CloudWatch. The recent metric history is the main focus of the graphs.

      • For Scaling metric, choose the desired scaling metric. If there are no other predefined metrics available, this option has no drop-down list to show.

      • For Target value, choose the desired target utilization value.

      • For Load metric [Auto Scaling groups only], choose an appropriate load metric to use for predictive scaling.

      • For Replace external scaling policies, choose whether to delete scaling policies created from outside of the scaling plan (such as from other consoles) and replace them with new target tracking scaling policies created by the scaling plan.

    3. (Optional) By default, predictive scaling is enabled for your Auto Scaling groups. To disable predictive scaling for your Auto Scaling groups, clear Enable predictive scaling.

    4. (Optional) By default, dynamic scaling is enabled for all resource types. To disable dynamic scaling for a type of resource, clear Enable dynamic scaling.

    5. (Optional) By default, when you specify an application source from which multiple scalable resources are discovered, all resource types are automatically included in your scaling plan. To omit a type of resource from your scaling plan, clear Include in scaling plan.

  3. When you are finished, choose Next.