In which cases is it advisable to apply vertical scaling of the system?

Vertical scaling of a system (scale-up) means increasing the resources of a single server — for example, adding CPU cores, RAM, or faster disks.

It is advisable to apply vertical scaling when:

• The system load is increasing, but the application's architecture does not support or makes it difficult to implement load distribution across multiple servers.
• There is a need to quickly increase performance without changing the code and infrastructure.
• The system is limited by the resources of a single node, and adding resources will significantly improve its performance.

However, vertical scaling has limits (physical and financial), and when these limits are reached, horizontal scaling (scale-out) should be considered.