AA dedicated application-services infrastructure providing secure communication, authN, and authZ
BA single load balancer that just distributes the incoming requests across the backend servers
CA message queue that buffers the events passed between two decoupled microservices
DA monitoring dashboard that charts the request latency across the whole of the cluster
Why this is the answer
A service mesh is a dedicated application-services infrastructure providing secure communication, authentication, and authorization for users, services, and devices — not just a load balancer, a message queue, or a dashboard.