This chapter aims to set you into a perspective where you will be able to see the evolution of the NoSQL paradigm. It will start with a discussion of common problems that an average developer faces when the application starts to scale up and software components cannot keep up with it. Then, we'll see what can be assumed as a thumb rule in the NoSQL world: the CAP theorem that says to choose any two out of consistency, availability, and partition-tolerance. As we discuss this further, we will realize how much more important it is to serve the customers (availability), than to be correct (consistency) all the time. However, we cannot afford to be wrong (inconsistent) for a long time. The customers wouldn't like to see that the items are in stock, but that the checkout is failing. Cassandra comes into picture with its tunable consistency.

We will take a quick peep into all the actions that go on when a read or mutate happens. This leaves...