Linkerd is a lightweight service mesh that manages service-to-service traffic, security policies, and telemetry without requiring application code changes—so B is correct. A service mesh introduces a dedicated layer for east-west traffic (internal service calls) and typically provides features like mutual TLS (mTLS), retries/timeouts, traffic shaping, and consistent metrics/tracing signals. Linkerd is known for being simpler and resource-efficient relative to some alternatives, which aligns with the “lightweight tool” phrasing.

Why this matches the description: In a service mesh, workload traffic is intercepted by a proxy layer (often as a sidecar or node-level/ambient proxy) and managed centrally by mesh control components. This allows security and traffic policy to be applied uniformly without modifying each microservice. Telemetry is also generated consistently because the proxies observe traffic directly and emit metrics and traces about request rates, latency, and errors.

The other choices don’t fit. NetworkPolicy is a Kubernetes resource that controls allowed network flows (L3/L4) but does not provide L7 traffic management, retries, identity-based mTLS, or automatic telemetry aggregation. kube-proxy implements Service networking rules (ClusterIP/NodePort forwarding) but does not enforce access policies at the service identity level and is not a telemetry system. Nginx can be used as an ingress controller or reverse proxy, but it is not inherently a full service mesh spanning all service-to-service communication and policy/telemetry across the mesh by default.

In cloud native architecture, service meshes help address cross-cutting concerns—security, observability, and traffic management—without embedding that logic into every application. The question’s combination of “traffic flows,” “access policies,” and “aggregates telemetry” maps directly to a mesh, and the lightweight mesh option provided is Linkerd.

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