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Difficulty: MediumScale Azure App Service Web Apps

You manage a memory-intensive web application named PatientPortalAPI that is currently hosted on a Shared (D1) App Service plan. During peak usage hours, the application experiences memory spikes exceeding 75%, causing it to become unresponsive. You must configure the application to dynamically scale out by adding instances when memory usage exceeds 75%, and automatically scale in when the load subsides. Which of the following actions should you perform to meet these requirements?

  1. A
    Scale up the App Service plan to the Basic (B1) tier, and then configure an autoscale rule with a scale-out threshold of 75% memory and a scale-in threshold of 50% memory.
  2. B
    Keep the App Service plan on the Shared (D1) tier, and then configure an autoscale rule with a scale-out threshold of 75% memory and a scale-in threshold of 50% memory.
  3. Scale up the App Service plan to the Standard (S1) tier, and then configure an autoscale rule with a scale-out threshold of 75% memory and a scale-in threshold of 50% memory.Answer
  4. D
    Scale up the App Service plan to the Standard (S1) tier, and then configure an autoscale rule with a scale-out threshold of 75% memory and a scale-in threshold of 80% memory.

Answer

Scale up the App Service plan to the Standard (S1) tier, and then configure an autoscale rule with a scale-out threshold of 75% memory and a scale-in threshold of 50% memory.
To configure autoscale rules, the App Service plan must be scaled up to at least the Standard (S1) tier, as the Shared (D1) and Basic (B1) tiers do not support autoscaling. Furthermore, to prevent autoscale flapping, the scale-in threshold must be set to a value significantly lower than the scale-out threshold. A scale-in threshold of 50% ensures that the resource consumption drops below a safe level before removing an instance, whereas a threshold of 80% is higher than the scale-out trigger (75%) and would cause immediate scale-in loop behavior.

Step-by-Step Solution

1
Determine the minimum App Service plan tier required to configure autoscale rules.
The Standard (S1) or higher pricing tier must be selected, as Shared (D1) and Basic (B1) tiers do not support autoscale rules.
Azure App Service autoscale rules require at least the Standard tier.
2
Determine the scale-in threshold that avoids autoscale flapping.
A scale-in threshold must be lower than the scale-out threshold and should account for the distributed load reduction on scaled-out instances.
If the scale-in threshold is too high (such as 80% when the scale-out threshold is 75%), the system will immediately scale in after scaling out, resulting in constant loop execution (flapping).
3
Select the correct pricing tier and threshold combination.
Scale up to the Standard (S1) plan and configure a scale-out threshold of 75% and a scale-in threshold of 50%.
This configuration satisfies all technical requirements and operates within valid operational thresholds.

Key Concept

Azure App Service plan tier scaling features and autoscale flapping prevention.
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Topics

Scale Azure App Service Web Apps

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