Reactive programming has been around for some time now, but recently has gained a new resonance, simultaneously with the rise of microservices and the ubiquity of multi-core processors: it represents a way of meeting the increasing demands of today, where applications need to have high availability and low response times also during high load. It avoids stateful programs, allowing the programmer to abstract away low-level threading, synchronization, and concurrency issues. However, reactive programming can represent the most appropriate choice only in peculiar scenarios, for instance when concurrency and asynchronicity are absolutely needed, or for handling large streams of data. The thesis is the result of the internship experience carried out at Technology Reply.