A Kubernetes controller automatically adds another pod replica to the resource pool in response to...

The Kubernetes controller is implementing horizontal scalability by adding another pod replica in response to increased application load. Horizontal scaling involves adding more instances of a service or application to handle the increased load, as opposed to vertical scaling, which would involve adding more resources (CPU, RAM) to a single instance. Horizontal scaling is a key feature of cloud-native applications and is supported by Kubernetes to ensure high availability and performance.