AZ-204 Develop Azure compute solutions Practice Question
Your company runs a critical web application on Azure App Service (Windows) that experiences intermittent high CPU usage. The application uses the Standard tier with auto-scaling based on CPU percentage. During auto-scale events, there is a delay of several minutes before new instances become available, causing temporary performance degradation. You need to reduce the latency of scaling out. What should you do?
⚠ Common exam trap
Many candidates assume upgrading the tier or changing the metric will solve scaling latency, but the real bottleneck is the cold-start time of the application itself, which 'Always On' directly mitigates.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable the 'Always On' setting in the App Service application settings.
The 'Always On' setting prevents the App Service from being unloaded after periods of inactivity, which reduces the cold-start latency when new instances are added during auto-scale events. Without 'Always On', idle instances may be recycled, causing delays of several minutes as the application re-initializes on new VMs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure auto-scaling to use HTTP queue length as the metric.
Why it's wrong here
Configuring auto-scaling to use HTTP queue length as a metric helps respond to increasing request backlogs by adding new instances. However, this metric primarily signals that existing instances are overwhelmed, triggering the provisioning of *new* instances. It does not inherently reduce the time it takes for those newly provisioned instances to start up and become responsive, which is the core issue of cold start latency. Therefore, while useful for load management, it doesn't directly address the initial startup delay.
- ✓
Enable the 'Always On' setting in the App Service application settings.
Why this is correct
Enabling the 'Always On' setting in Azure App Service ensures that the web application process is kept loaded and running, even during periods of inactivity. By preventing the application from being unloaded or idled out due to lack of traffic, it significantly reduces or eliminates the "cold start" latency that occurs when the application needs to be reloaded from scratch. This keeps the application immediately responsive to incoming requests, which is crucial for critical web applications.
- ✗
Upgrade the App Service plan to the Premium tier.
Why it's wrong here
Upgrading the App Service plan to the Premium tier provides access to more powerful underlying hardware, enhanced networking capabilities, and additional features like VNet integration or private endpoints. While these resources can improve overall application performance and capacity, they do not inherently prevent the application process from being unloaded due to inactivity. Consequently, a Premium tier upgrade alone will not eliminate the cold start latency that occurs when an idle application needs to be reinitialized.
- ✗
Change the auto-scale metric to memory percentage instead of CPU.
Why it's wrong here
Changing the auto-scale metric from CPU percentage to memory percentage, or any other resource-based metric, primarily dictates the conditions under which new instances are added to the App Service plan. While optimizing scaling triggers is important for resource utilization and responsiveness under load, it does not influence the inherent startup time of an individual application instance. The cold start issue is related to the application's initial loading and initialization sequence, which is unaffected by the choice of auto-scaling metric.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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