Project Reactor is capable of providing an API support for specific data cardinality, ranging from generating endless streams to publishing just a single data entry.

Instead of waiting for the entire data stream to process, Project Reactor enables the subscribers to handle the elements of a stream as they arrive. This makes the data processing operation more flexible and optimized by improving resource utilization. The memory required to be allocated to a subscriber is limited because data processing happens in a subset of items arriving at a particular time, rather than processing entire data streams in one go. Also, this makes the system more responsive as the results will start as soon as the first set of elements is received, instead of waiting until all items have been received and processed to deliver a final output.