Match isolation to trust: namespaces for friends, node groups for strangers, clusters for regulators.

Soft

Namespace per tenant

RBAC through access entries and RoleBindings.
ResourceQuota and LimitRange.
Default-deny NetworkPolicy.
Pod Identity per ServiceAccount.
Pod Security Standards.

Cheapest. Shared control plane and nodes.

Partial hard

Node pool per tenant

Everything on the left plus taints, tolerations and node affinity.
Tenants never share a node.
Dedicated Karpenter NodePool per tenant.

Higher cost from lower bin-packing.

Hard

Cluster per tenant

Separate control plane and data plane.
Clear blast-radius and compliance boundary.
Often one AWS account per tenant too.

Highest cost and operations effort.

Default to soft

For trusted internal teams, namespaces with quotas, policies and per-namespace identity are the standard, least expensive choice.

Escalate for a reason

Move to dedicated nodes or clusters only for untrusted tenants or hard compliance boundaries. Deck 5 covers Capsule, vCluster and sandboxed runtimes.

Sharing a cluster: three tenancy models on EKS

When several teams share an EKS cluster, you choose how strongly to isolate them. Soft multi-tenancy gives each tenant a namespace, with RBAC (granted through access entries and RoleBindings), resource quotas, default-deny network policy, per-ServiceAccount Pod Identity roles and Pod Security Standards. It is the least expensive model and is designed for teams that trust each other not to attack the platform, though a noisy neighbour can still affect others.

Partial hard multi-tenancy adds node-level separation: taints and tolerations or node affinity so that a tenant's Pods only run on its own nodes, typically through a dedicated Karpenter NodePool or managed node group. It prevents sharing a kernel but costs more through reduced bin-packing. Hard multi-tenancy gives each tenant its own cluster (and often its own AWS account) for the strongest blast-radius and compliance boundary, at the highest operational cost.

The default recommendation is the cheapest model that satisfies the actual trust boundary. Pay for stronger isolation only when you have an untrusted tenant or a regulatory requirement that soft isolation cannot meet.

Deck 5 covers these models in depth with tenant-aware tools (Capsule), virtual clusters (vCluster) and sandboxed runtimes (gVisor, Kata).