Elastic

Reactive systems should be elastic, so they effectively apply the scalability principle to stay responsive under varying workloads, but more internally, the system itself may have the capability of increasing or decreasing the resources that allocate.

In the older architecture, planning resources was part of our architecture; we design thread pools to handle our request with certain capacity, and we prepare our servers to be able to manage this.

In reactive systems, our services could dynamically fetch more resources if required and free them when they are not needed.