Description

Move one or more EC2 instances in an Auto Scaling Group (ASG) into Standby. Instances in Standby are detached from load balancers and do not receive traffic; the ASG can launch replacement instances if desired capacity is maintained. You can choose whether to decrement desired capacity by the number of instances moved to standby. This action is useful for:

Rotating instances out of an ASG during incident response (e.g., move to standby, wait for replacement, then terminate)
Taking instances out of service for maintenance or troubleshooting without terminating them
Building runbooks that combine with Set Instance Protection, Describe Auto Scaling Instances, and Terminate Instance in Auto Scaling Group
Letting the ASG launch replacement instances before terminating the old one when Should Decrement Desired Capacity is set to false

Instructions

Inputs

Name	Description
Integration	Select a Workflow Integration or click New AWS Connection to establish a new one.
Auto Scaling Group Name	The name of the Auto Scaling Group that contains the instances.
Instance IDs	One or more EC2 instance IDs to move to Standby (comma-separated). Can be from a prior step (e.g., Describe Auto Scaling Instances) or from incident custom details.
AWS Region	The AWS region where the ASG is located. If left blank, the action uses `us-east-1` as the default.
Should Decrement Desired Capacity	Whether to reduce the ASG's desired capacity by the number of instances moved to standby. Set to false (default) to keep capacity so the ASG launches replacements; set to true to shrink the group.

Outputs

Name	Description
Activities	JSON array of Auto Scaling activity records returned by the API for the Enter Standby operation.
Placed In Standby	Array of instance IDs that were successfully placed in Standby.
Result	Whether the action succeeded: Success or Failed.
Result Summary	Brief description of what the action did or if it failed.
Error	Error message, if the action failed.

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Tips

Instance Rotation: For instance-rotation runbooks, use Should Decrement Desired Capacity = false so the ASG launches a replacement before you terminate the instance in a later step.

Chaining Actions: Use the Auto Scaling Group Name and Instance IDs from Auto Scaling: Describe Auto Scaling Instances so the workflow works when the incident only provides an instance ID.