This is more of work in progress , which tries to cover some of the key terms that are used in scaling systems and what do they really mean.

Backpressure : When the server becomes overwhelemed with the high volume of client requests, in such cases how exactly does the server behave

Fan in Fan Out : This is more relevant from some of the social networks perspective like facebook, twitter. How does the update from celebrity flow to its followers or a popular event reaches .