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EKS Auto Mode - Considerations

In the introductory blog on Auto Mode for Amazon EKS, we described the basics of this new capability that was announced at AWS re:Invent 2024. In this blog, we will review considerations that organizations need to factor in before using EKS in Auto Mode.

Note

Please consider this as a living/evolving document. EKS Auto Mode is relatively new and we update this blog with new learnings/findings.

Considerations for EKS Auto Mode

Pros

Some of the advantages of Auto Mode for Amazon EKS are described below.

Operational Overhead

By offloading day-to-day, low level cluster management operations to AWS, Ops teams can focus their time on other critical tasks.

Automated Patching

The core add-ons (i.e. vpc-cni, Karpenter, core-dns, ebs-csi etc) are automatically patched and kept up to date by AWS in their management plane.

Cost Efficiency

By dynamically scaling resources based on actual demand, EKS Auto Mode can help minimize costs.

Cons

These are an initial list of constraints that organizations need to consider as they make the decision on whether EKS Auto Mode is a good fit for them or not.

Custom AMIs

Custom AMIs are not supported in Auto Mode. All the infrastructure including the Amazon Machine Image (AMI’s) used for the nodes are fully managed by AWS. This means that Auto Mode uses predefined AMIs optimized and maintained by AWS for Kubernetes workloads. This allows AWS to automatically update, patch AMIs as part of the managed service.

This also means you cannot specify or override the default AMIs used for Auto Mode. This also means that users do not have direct access to the nodes via SSH or SSM access.

If you require custom AMIs because of your internal security requirements, managed node groups with standard EKS clusters are a better fit.

Custom CNIs

Many enterprises have standardized on eBPF because of enterprise grade security and observability requirements. They prefer to use 3rd party CNIs such as Cilium and Calico that have turnkey support for eBPF.

With EKS Auto Mode, the CNI is locked to the AWS VPC CNI.

Cost

Auto Mode for EKS is not free. Users should plan to pay a significant premium for EKS clusters operating in Auto Mode. Just like many organizations are willing to pay a premium for managed services such as ECS or Fargate (i.e. these are very expensive relative to vanilla EC2), some organizations may consider this to be a fair exchange because they can offload a bunch of busy work to AWS and focus on other items in their backlog.

In a nutshell, enabling EKS Auto Mode incurs an extra management fee based on the type and duration of Amazon EC2 instances managed by Auto Mode. In the example on AWS's pricing page for EKS, you can see that the application uses a mix of c6a.2xlarge, c6a.4xlarge, m5a.2xlarge, and m5a.xlarge instance types. For this example, the additional management charges for Auto Mode is $125/month.

EKS Auto Mode Pricing

On average, users should assume you will need to pay an additional 12-15% fee to AWS for using Auto Mode.

Conclusion

Auto Mode for EKS is a significant step towards what a true managed Kubernetes service should look like. As with any offering, there are Pros and Cons. We recommend organizations review the considerations carefully before making the leap to Auto Mode. Organizations may also benefit from the best of both worlds by using EKS Auto Mode clusters with managed node groups. These are referred to as mixed-mode clusters.

Important

Organizations interested in trying this out using Rafay, we will be publishing a follow on blog where we will walk through step-by-step instructions. We also plan to publish a video walkthrough of this later this week.