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One Kubernetes cluster or many: isolation, blast radius and cost compared

We ran everything in one big Kubernetes cluster until a CRD upgrade broke three teams at once. This guide compares one shared cluster, a cluster per environment and a cluster per team on isolation, blast radius, upgrade effort and real cost, with a worked cost model.

John Nguyen @devbugs · February 22, 2025 · 9 min read · 33 Views

Banner: one large shared cluster compared with several smaller isolated clusters

For two years our company ran production on a single Kubernetes cluster. Nine teams, around 140 services, one control plane. It was cheap and simple, until a cert-manager upgrade changed a CRD version that two other teams' charts still referenced, and an unrelated node pool rotation the same afternoon took a shared ingress controller down with it. Three teams lost an evening, and the post-incident review came back with one question: should we split the cluster? That question gets asked a lot and...

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#kubernetes #argocd #eks #multi-tenancy #multi-cluster

Written by

John Nguyen @devbugs

I am a Senior Software Engineer with over a decade of hands-on experience building, scaling, and maintaining complex systems across the full stack—spanning frontend, backend, and DevOps. Over the last 10 years, I have navigated diverse architectures and untangled some of the most frustrating, elusive bugs in production. I believe that every production incident is a massive learning opportunity. Having discovered hibug.me, I am excited to contribute to this knowledge base, breaking down root causes, and sharing verified fixes to help fellow developers debug faster and build more resilient systems.

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