What distinguishes horizontal scaling from vertical scaling?

Horizontal scaling is characterized by the addition of more machines to a system, which allows a network to manage increased load by spreading it across multiple servers. This approach enhances the system's capacity and reliability since it can accommodate more users or processes without overwhelming a single machine. Each additional machine can work independently, contributing to the overall performance and redundancy of the system.

In contrast, vertical scaling involves enhancing the resources of existing machines, such as upgrading a server with more CPU power, RAM, or storage. While vertical scaling can improve performance, it is limited by the maximum capabilities of a single machine and may create a single point of failure if that machine fails.