reading about Context in Reactor, in order to simulate the variables we used to set in ThreadLocal scope, Reactor has the concept of Context. I attach below an image of the reactor documentation about this Context and an example. Its said that this Context is set to the Subscriber object that is created during subscription. Its said too that this Subscriber goes from downstream to upstream because it cannot be other way in order for the Producer to have this Subscriber in order to call it. Along the way the Subscriber flows from bottom to top in the pipeline its executed first the contextWrite methods in order to set the Context in the created Subscriber.