Which configuration involves adding more server instances in response to specific events?

The correct answer involves scaling horizontally based on an event. This approach is focused on adding more server instances to handle increased demand triggered by specific events, such as traffic spikes or increased workload, allowing for better resource management and responsiveness in cloud environments.

Horizontal scaling, or scaling out, typically involves deploying additional instances of a service when certain criteria are met. This configuration ensures that as demand rises, you can quickly distribute the load across multiple servers, enhancing performance and availability. It is particularly beneficial for applications designed to operate in a distributed manner, ensuring that no single instance becomes a bottleneck.

While auto-scaling generally refers to the automatic adjustment of resources based on real-time metrics and predefined policies, the specific concept of adding server instances in response to particular events aligns closely with horizontal scaling based on those events. Vertical scaling, on the other hand, involves adding resources (like CPU or RAM) to an existing server rather than adding new servers. Scheduled scaling refers to predetermined scaling actions based on time, rather than real-time events.