Service Mesh is correct because it is the technology specifically designed to connect and manage communication between hundreds or thousands of services across clusters while providing load balancing, traffic management and observability.

This approach deploys lightweight proxies alongside application containers to handle east west traffic and to collect telemetry without changing application code. A control plane programs those proxies and enables features such as fine grained routing, retries, circuit breaking, mutual TLS and distributed tracing across multiple clusters which together provide the traffic management and observability described in the question.

Ingress Controller is focused on north south traffic entering a cluster and on routing external requests to services inside a cluster, and it does not provide the mesh style sidecar proxies or the full interservice observability and cross cluster traffic control that a service mesh provides.

StatefulSet is a workload API used to manage stateful applications that require stable network identities and persistent storage, and it is not a networking layer for service to service traffic management or observability.

Kubernetes Deployment manages rollout, scaling and updates for stateless pods, and it does not provide advanced traffic routing, distributed telemetry or security features for interservice communication that are offered by a service mesh.

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