Horizontal and Vertical scaling

Horizontal scaling:

Horizontal scaling means that the scaling is done by adding more machines into your pool of resources

Vertical scaling:

Vertical scaling means that the scaling is done by adding more power (CPU, RAM) to an existing machine.

Example of Horizontal and Vertical scaling:

Horizontal scaling is often based on data partitioning and each node contains only part of the data. The vertical scaling resides on a single node and scaling is done through multi-core by spreading the load between the CPU and RAM resources of that machine.