In Chapter 5, Reactive Manifesto, we observed the importance of being message-driven for being resilient. Let's consider a simple real-life scenario while building applications and let's understand the role of messages.
Let's assume we are building an image-sharing social networking site (such as Instagram). Users would upload pictures from their mobile phones and share them with their friends and followers. A simplified view would be as follows:
Of course, there would be many other background services, but let's consider a cropped-down version for simplicity.
Once the user shares a picture on his mobile app, the following steps ...