What other scaling methods exist besides horizontal?

In addition to horizontal scaling (scale-out), which involves adding new nodes or instances to distribute the load, there is vertical scaling (scale-up). It involves increasing the resources of a single server: adding CPU, memory, disk space.

Vertical scaling is easier to implement as it does not require changes to the application's architecture, but it has physical limitations and can be more expensive.

There are also concepts:

• Load-based scaling (dynamic scaling) — automatic addition or removal of resources depending on the current load.

• Functional scaling — dividing the application into microservices that scale independently.

• Data scaling — sharding databases to distribute the load.

An example of vertical scaling: increasing the RAM of a database server to improve performance without adding new servers.