CAS-004 Security Architecture Practice Question
A security architect at a financial services firm is designing the network segmentation for a new containerized trading platform running on Kubernetes. The platform must isolate workloads so that a compromise of the public-facing web tier cannot directly reach the database tier. The architect wants to enforce this isolation natively within the cluster and have policies applied automatically as new pods are scheduled. Which of the following should the architect implement?
⚠ Common exam trap
The trap here is assuming that encrypting service traffic with a mesh also restricts which services can communicate, when encryption and authorization are separate controls.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
NetworkPolicies applied to namespaces and selected pods
Kubernetes NetworkPolicies provide label-based, pod-level segmentation enforced by the CNI plugin, so isolation follows workloads wherever they are scheduled. The architect can default-deny traffic in a namespace and then allow only the specific web-to-API and API-to-database flows, which prevents a compromised front end from reaching the database tier. Encryption and edge controls address different concerns and do not restrict lateral movement inside the cluster.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
NetworkPolicies applied to namespaces and selected pods
Why this is correct
Kubernetes NetworkPolicies are the native mechanism for pod-level segmentation. They select pods via labels and define ingress and egress rules that allow or deny traffic between namespaces, pods, and CIDR blocks. Because the CNI plugin enforces them dynamically, newly scheduled pods that match a label selector inherit the policy automatically, giving the architect the isolation and automation required without external appliances.
- ✗
A service mesh with mutual TLS between all sidecars
Why it's wrong here
A service mesh with mTLS encrypts and authenticates service-to-service traffic, which improves confidentiality and identity, but it does not by itself deny unauthorized paths. Without authorization policies, a compromised web pod could still open a connection to the database tier and present a valid certificate. The scenario requires enforcement of which flows are permitted, not merely encryption of the flows that occur.
- ✗
VLAN segmentation on the underlying hypervisor
Why it's wrong here
VLANs operate at Layer 2 and segment physical or virtual network segments, not individual pods. In Kubernetes, pods frequently share node interfaces and can be rescheduled anywhere, so VLAN boundaries do not follow workloads and cannot enforce pod-to-pod isolation. The architect needs a control that understands pod identity and labels, which VLANs do not provide.
- ✗
An ingress controller with TLS termination and WAF rules
Why it's wrong here
An ingress controller manages north-south traffic entering the cluster and can terminate TLS or inspect HTTP requests, but it does not govern east-west traffic between internal tiers. A compromised web pod communicating directly with the database would bypass the ingress path entirely. The requirement is internal workload isolation, so an edge-focused control does not satisfy the scenario.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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