Back pressure

Back pressure is produced when a reactive system is published at a rate higher than the subscriber could handle, in other words, this is how a consumer of a reactive service says: Please, I am not able to deal with the demand at the moment, stop sending data and do not waste resources (for example, buffer memory).

There is a range of mechanisms for handling this, and they are usually close to the reactive implementation, from batching the messages to dropping them, but right now, we don't need to get into the details, just understand that any reactive system must deal with back pressure.