Certified Kubernetes Application Developer (CKAD) Practice Test

What is a defining characteristic of a headless service in Kubernetes?

1. It has no external IP address

2. It requires a load balancer configuration

3. It automatically scales Pods based on traffic

4. It provides persistent storage for stateful applications

The correct answer is: It has no external IP address

A defining characteristic of a headless service in Kubernetes is that it does not have an external IP address. Instead of routing traffic through a single IP address, a headless service allows you to directly access the individual Pods that are backing the service. This is accomplished by omitting the ClusterIP parameter, which results in the service not being assigned an IP. As a consequence, DNS queries for the service return the IP addresses of the individual Pods rather than a single virtual IP. This functionality is particularly useful for scenarios where you want to make direct connections to specific Pods for purposes such as stateful applications or when you need more control over how traffic is distributed. The other options involve characteristics or functionalities that do not pertain to a headless service. For instance, a load balancer configuration is not necessary for a headless service, automatic scaling of Pods is managed through other mechanisms like Horizontal Pod Autoscalers, and persistent storage is managed through storage classes and StatefulSets rather than being a feature of a headless service specifically.