The most effective strategy to minimize costs for a workload with predictable peak and off-peak times (such as standard business hours) is to reduce the allocated resources during the off-peak period. Creating an Azure Automation runbook to automatically resize the virtual machines to a smaller, less expensive size outside of business hours directly addresses this requirement. This is a form of scheduled vertical scaling (scaling down) that ensures you are not paying for unneeded capacity during periods of low demand.

B. Configure the Scale Up settings for a web app.

This is typically a manual, one-time change of an App Service Plan's pricing tier and is not an automated, recurring strategy for daily cost optimization.

C. Deploy a virtual machine scale set that scales out on a 75 percent CPU threshold.

This describes reacting to high load by adding more instances (scaling out), which increases cost. It does not address the primary goal of reducing costs during predictable low-traffic periods.

D. Configure the Scale Out settings for a web app.

This applies to Azure App Services (PaaS), not virtual machines (IaaS). While it can be used for scheduled scaling, option A is specific to the virtual machine context implied by the answer choices.

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1. Azure Automation Overview: Official documentation states that a common use case for Azure Automation is to "Start and stop resources on a schedule. Shut down VMs during off-hours and turn them on in the morning for your dev/test environments." Resizing is a similar

supported operation.

Source: Microsoft Learn

"Azure Automation overview"

Section: "Process automation".

2. Resize a Virtual Machine: The official documentation confirms that virtual machines can be resized to change their CPU

RAM

and other properties

which directly impacts their cost. It also notes this can be automated.

Source: Microsoft Learn

"Resize a virtual machine"

Section: "Resize a VM".

3. Overview of Autoscale in Microsoft Azure: This document distinguishes between horizontal scaling (changing the number of instances

as in options C and D) and vertical scaling (changing the size of instances

as in option A). For predictable workloads

scheduled scaling is a key cost-management feature.

Source: Microsoft Learn

"Overview of autoscale in Microsoft Azure"

Section: "Horizontal vs. vertical scaling".