What does it mean to scale vertically based on current load?

Scaling vertically based on current load refers specifically to increasing the resources of a single server as needed. This could involve upgrading the existing hardware by adding more CPU power, increasing RAM, or enhancing storage capacity.

The main concept of vertical scaling, also known as "scaling up," is essentially about enhancing the capabilities of an individual server to handle increased workload demands. When the application experiences higher traffic or resource requirements, instead of adding more servers (which would be horizontal scaling), the existing server's capacity is improved. This method can be more straightforward for certain applications since it doesn’t require changes to the distributed architecture or involve load balancing across multiple servers.

For example, if your server is running a web application and you notice that it is becoming slow during high traffic periods, vertically scaling would mean upgrading the server's hardware to ensure it can handle more simultaneous users without performance degradation.

In contrast, the other choices involve strategies that relate to horizontal scaling, which is focused on adding more servers or distributing loads rather than enhancing individual server capabilities.