Upgrading Kubernetes—whether self-managed or on Amazon EKS—is an essential yet often underestimated aspect of cluster lifecycle management. It’s not just a matter of keeping up with new features, but also about ensuring compatibility, security, and performance for the workloads running in your environment.

While managed services like EKS simplify some of the heavy lifting, the upgrade process still demands careful planning and execution. At Kapstan, we’ve seen how upgrades can introduce both opportunities and operational risks. This blog explores key considerations and practices for effective Kubernetes and EKS upgrades—minus the vendor hype.

Why Kubernetes Upgrades Matter

Every Kubernetes release introduces improvements in areas like API stability, performance, and security. More importantly, each version has a limited support window—typically one year for open-source Kubernetes and slightly longer for managed services like EKS. Ignoring upgrades leads to deprecated APIs, outdated security patches, and potential incompatibility with modern tooling.

For organizations adopting GitOps, CI/CD, and service mesh strategies, staying current with Kubernetes versions becomes essential for maintaining compatibility across the stack.

The Evolving Nature of EKS Upgrades

Amazon EKS provides a managed control plane, which simplifies version upgrades compared to self-hosted clusters. But that doesn’t eliminate complexity entirely. While AWS handles the control plane, you remain responsible for upgrading worker nodes, validating workloads, and ensuring that cluster-wide components (like CNI plugins, Ingress controllers, and custom CRDs) remain compatible.

EKS generally supports three Kubernetes versions at a time. As each version approaches end-of-life, AWS sends out notifications, but the burden of action remains with the user. This becomes more challenging in environments with multiple clusters, managed add-ons, or custom networking configurations.

Common Pitfalls During Upgrades

1. Neglected API Deprecations

Every Kubernetes upgrade cycle includes API deprecations. Upgrading without auditing your workloads can lead to runtime failures. Controllers and CRDs that rely on deprecated APIs may stop functioning entirely.

2. Incompatible Add-ons

Add-ons such as CoreDNS, kube-proxy, and the Amazon VPC CNI often have version constraints. Upgrading Kubernetes without updating these components can result in networking failures or misbehavior at the control plane level.

3. Disruption of Stateful Workloads

Kubernetes upgrades can impact StatefulSets, persistent volumes, and pod disruption budgets. Without sufficient node drainage planning, these workloads may experience unplanned downtime.

4. Missed Drain Events

If you're using self-managed worker nodes or a custom lifecycle controller, draining nodes incorrectly during an upgrade can lead to data loss or dropped requests. EKS Managed Node Groups help here, but they still require validation post-upgrade.

Kubernetes Upgrade Strategy for Production Clusters

At Kapstan, a successful Kubernetes or EKS upgrade strategy often follows a few key principles:

1. Baseline Inventory

Begin with a full audit of the existing cluster state. What APIs are in use? Are workloads pinned to specific Kubernetes versions? Is your infrastructure-as-code aligned with the desired upgrade path?

2. Staging Environment First

Run the upgrade through a staging or non-production environment first. This isn’t just about validation—it’s about identifying behavioral changes that may not surface in static code analysis.

3. Upgrade in Layers

Don’t attempt to upgrade everything at once. Control plane, node groups, system add-ons, and workloads should be upgraded incrementally. Each step should involve monitoring, rollback plans, and regression testing.

4. Plan for Downtime, Avoid It If Possible

Even though Kubernetes is designed to be resilient, upgrades can introduce momentary instability. Consider leveraging surge deployment strategies or temporarily relaxing disruption budgets to maintain availability.

Specific Considerations for EKS

While AWS handles the control plane upgrade in EKS, there are unique nuances:

• Managed Node Groups: AWS offers a rolling update mechanism, but workloads should still tolerate disruption.

• Fargate Support: Ensure compatibility of workloads with the Fargate runtime before attempting upgrades.

• EKS Add-ons: Monitor version compatibility for add-ons like CoreDNS, kube-proxy, and CNI. These may lag behind Kubernetes versions and require manual updates.

• IAM Roles and Policies: Some upgrades introduce new features that require policy adjustments, especially around access to node services or container registry behaviors.

Observability During and After Upgrade

Metrics and logs become critical during any upgrade cycle. Use tools like Prometheus, Grafana, CloudWatch, and Fluent Bit to watch for:

• Pod evictions or restart loops

• API server request failures

• Node conditions or NotReady states

• CNI or DNS resolution issues

Post-upgrade, ensure that autoscalers, ingress controllers, and admission webhooks are functioning as expected.

What We’ve Learned at Kapstan

Across client environments, we’ve seen that upgrades aren’t just technical operations—they’re architectural checkpoints. Kubernetes upgrades prompt a reflection on cluster design, workload efficiency, and operational maturity.

EKS upgrades, while simpler in execution, still require robust planning and systems-level thinking. By viewing upgrades as part of continuous infrastructure evolution—rather than a fire drill triggered by end-of-support warnings—teams stay more resilient and performant over time.

Conclusion

Upgrading Kubernetes or EKS isn’t just about “staying current”—it’s about reducing operational risk, ensuring API compatibility, and unlocking performance and security enhancements. Whether you manage a single dev cluster or dozens of production environments, a thoughtful upgrade process is part of running Kubernetes at scale.

Kapstan continues to observe that teams with well-documented upgrade playbooks and continuous validation pipelines consistently outperform those treating upgrades as one-off events. As Kubernetes continues to evolve rapidly, your infrastructure must evolve with it—methodically, safely, and deliberately.