What is the technology called that allows scaling server resources without increasing the number of containers or application instances?

The technology that allows scaling server resources without increasing the number of containers or application instances is called horizontal scaling or vertical scaling.

In this context, if it specifically refers to scaling the resources of a single instance (e.g., CPU, RAM) without adding new containers, then it is — vertical scaling (vertical scaling, or scale-up).

Example: increasing the allocated memory and CPU cores for an existing container or virtual machine.

Unlike horizontal scaling (scale-out), where new instances are added to distribute the load, vertical scaling increases the capacity of the already running instance.