What is meant by the concept of horizontal scaling of a system?

Horizontal scaling — this is a way to increase system performance by adding new nodes (servers) to a cluster. Instead of improving a single powerful server (vertical scaling), the system is expanded by multiple identical or similar machines that collectively handle the load.

Advantages of horizontal scaling:

• Increased fault tolerance (if one node fails, others continue to operate)
• Flexibility and scalability
• Ability to distribute load

Example: a web application serving many users is run on multiple servers behind a load balancer.