LFCA Question #23: Real Exam Question with Answer & Explanation

Question

An IT associate has a web application running on multiple servers, configured to scale based on CPU usage. The current configuration has a minimum size of 1 and a maximum size of 5 servers, designed to launch and spread the instances across 3 Availability Zones (AZ). During a low utilization period, an entire AZ went down, and the application experienced downtime. What can the IT associate do to increase the availability of the application?

Options

• AIncrease the minimum to 2
• BChange to scale based on number of requests
• CDecrease the AZs to 2
• DIncrease the maximum to 6

Explanation

To enhance application availability during an Availability Zone outage, especially in a low utilization period where minimum scaling rules apply, ensuring more active instances are spread across zones is crucial. Increasing the minimum server count ensures that even when an AZ fails, remaining AZs have at least one active instance, preventing total application downtime.

Common mistakes.

• B. Changing the scaling metric might optimize for performance under load but does not directly address the issue of maintaining availability during an AZ outage when operating at minimum capacity.
• C. Decreasing the number of Availability Zones to 2 would reduce redundancy and further decrease availability, making the application more susceptible to outages if one of the two remaining AZs fails.
• D. Increasing the maximum server count addresses scaling for high demand, but it does not guarantee availability during low utilization or when an AZ fails if the minimum instance count remains at 1.

Concept tested. Cloud auto-scaling for high availability

Reference. https://docs.aws.amazon.com/autoscaling/ec2/userguide/AutoScalingGroupLifecycle.html

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