The scenario describes sporadic peak loads that occur only a few times a year. The most resource-efficient solution is to dynamically scale resources only when this peak load occurs. A horizontal autoscaling policy achieves this by automatically adding more CloudHub workers when a predefined metric, such as CPU utilization, exceeds a threshold. This distributes the increased request volume across more workers, maintaining performance under load. When the peak subsides, the policy automatically scales down the number of workers, ensuring that the company only pays for the extra capacity when it is actually needed, thus providing the most resource-efficient solution.

A. Permanently increasing worker size is not resource-efficient, as the larger, more expensive workers would be significantly underutilized during normal traffic periods.

B. While autoscaling is the correct approach, horizontal scaling (adding more workers) is generally more effective for handling increased request throughput than vertical scaling (increasing worker size).

C. Permanently increasing the number of workers is not resource-efficient. The additional workers would be idle and incur unnecessary costs for the majority of the year.

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1. MuleSoft Documentation, "Autoscaling":

Reference: "Autoscaling enables you to configure your application to automatically adjust the number of workers allocated to it based on the CPU load or memory usage. This feature is useful for applications that have variable load requirements over time... By using autoscaling, you can reduce the costs of running your applications by ensuring that you are only paying for the resources you need at any given time."

Location: MuleSoft Docs > CloudHub > Fabric > Autoscaling.

2. MuleSoft Documentation, "Configure Autoscaling Policies":

Reference: This document details the configuration of autoscaling policies, including setting up CPU-based triggers. It states, "You can configure a policy to scale out (add workers) when CPU utilization is above a certain threshold." This directly supports the mechanism described in the correct answer.

Location: MuleSoft Docs > CloudHub > Fabric > Configure Autoscaling Policies > CPU-Based Triggers section.

3. MuleSoft Documentation, "CloudHub Workers":

Reference: The documentation on workers explains the two scaling methods: "Horizontal scaling is achieved by adding more workers to your application... Vertical scaling is achieved by changing the size of the worker." For handling increased concurrent requests, horizontal scaling is the standard practice.

Location: MuleSoft Docs > CloudHub > Architecture > CloudHub Workers > Worker Sizing and Scaling section.