What is the purpose of labels in a Service?

• A. They enable a Service to select pods via selectors and route traffic to them.
• B. Labels specify how the service should route between nodes.
• C. Labels store secrets for the service.
• D. Labels define the traffic routing algorithm in the service.

Answer: (A)

Labels are key-value pairs attached to pods (and other objects) to tag and group them for selection. A Service uses a label selector to identify which pods should receive traffic, and the set of pods matching that selector becomes the endpoints the Service routes to. As pods start, scale, or be replaced, matching pods appear or disappear, and traffic is automatically directed to the current set. Labels do not store secrets, do not define routing between nodes, and do not determine routing algorithms; those aspects are handled by other mechanisms. So the purpose is to enable a Service to select pods via selectors and route traffic to them.