Certified Kubernetes Application Developer (CKAD) Practice Test

The most effective way to increase the replica count of a Deployment is through the use of the scale command. The `kubectl scale deployment` command is specifically designed for adjusting the number of replicas for a given Deployment. This command allows users to easily and directly increase or decrease the number of pod replicas that are running, which can help ensure that there are enough instances to handle the workload.

When the scale command is executed, Kubernetes will manage the lifecycle of pods automatically. It will create new pod instances if the replica count is increased or terminate existing ones if the count is decreased, ensuring that the desired state you specify is achieved and maintained.

Other methods mentioned focus on different aspects of modifying Deployments, but are not tailored specifically for changing the replica count. For instance, using the update command is generally meant for updating other properties of the Deployment, such as the container image or environment variables, rather than just scaling. The modify command does not exist as a specific command in the `kubectl` toolkit, and while you can change replicas using the set command, it lacks the direct clarity of intent and simplicity provided by the scale command.