Which of the following is NOT a valid state for a scaling activity in Alibaba Cloud's Elastic Scaling Service?

The correct choice reflects an understanding of the valid states for a scaling activity within Alibaba Cloud's Elastic Scaling Service. The valid states represent the various stages of a scaling operation, and each corresponds to a specific status that can occur during the process.

"In Progress" indicates that the scaling operation is currently being executed. This is a dynamic state showing that the service is actively working on scaling the resources.

"Success" represents a state where the scaling operation has completed successfully, meaning that the required adjustments to the resources (either scaling up or down) have been effectively achieved.

"Cancelled" denotes a situation where the scaling request has been aborted before completion, either by user action or system decision. This state shows that the intended scaling operation will not proceed.

In contrast, "Timeout" is not a valid state used to describe a scaling activity. Whereas a timeout might indicate a failed operation due to delays or issues, it is not officially recognized as a distinct state within the Elastic Scaling Service framework. Therefore, this option stands out as it does not align with the defined operational states of scaling activities.