A company runs container applications by using Amazon Elastic Kubernetes Service (Amazon EKS) and the Kubernetes Horizontal Pod Autoscaler. The…

The scenario describes a situation where the Horizontal Pod Autoscaler (HPA) is scaling pods, but the underlying EC2 nodes are not scaling to accommodate them. The Kubernetes Cluster Autoscaler is the purpose-built component designed to solve this exact problem. It integrates with the Kubernetes scheduler and the AWS EC2 Auto Scaling group that manages the EKS nodes. When it detects pods that cannot be scheduled due to insufficient resources on existing nodes, it automatically increases the desired capacity of the Auto Scaling group to add new nodes. This is the standard, most efficient, and lowest-overhead method for node autoscaling in EKS.

A. This option describes a scaling metric (memory usage) but fails to specify the automated mechanism needed to scale the nodes, which is the core requirement.

C. Using a custom AWS Lambda function would require significant development and maintenance effort, which contradicts the requirement for the LEAST administrative overhead.

D. An Amazon EC2 Auto Scaling group by itself scales based on EC2 metrics (like CPU utilization), not on Kubernetes-specific events like pending pods. It needs the Cluster Autoscaler to bridge this gap.

1. AWS Documentation

Amazon EKS User Guide

"Cluster autoscaling": "The Kubernetes Cluster Autoscaler automatically adjusts the number of nodes in your cluster when pods fail to launch due to lack of resources or when nodes in the cluster are underutilized... The Cluster Autoscaler is typically installed as a Deployment in your cluster." This document explicitly identifies the Cluster Autoscaler as the solution for automatic node adjustment based on pod scheduling needs.

2. AWS Documentation

Amazon EKS User Guide

"Managed node groups"

Section: "Node scaling": "The node Auto Scaling group for a managed node group can't be scaled to zero nodes... To enable the cluster autoscaler to scale a managed node group

you must tag the node Auto Scaling group..." This section confirms that the Cluster Autoscaler is the component that works with the underlying Auto Scaling group to manage node scaling.

3. GitHub

Kubernetes Autoscaler

"Cluster Autoscaler on AWS": "Cluster Autoscaler for AWS provides integration with Auto Scaling Groups. It enables users to choose from four different options of deploying a cluster-autoscaler..." This is the official project documentation

referenced by AWS

detailing the function and integration of the Cluster Autoscaler with AWS infrastructure.