When data does not fit on one computer
One problem that may occur is that we simply can't store the data on one computer and/or we still need to search for things on this dataset. To solve this kind of problem, we may need distributed Not only SQL (NoSQL) databases, such as Cassandra. Cassandra supports data distribution on multiple systems where availability and performance are critical:


Cassandra tries its best to not have a single point of failure. For example, all nodes will act like a sort of master (there is no actual master) so that all nodes have the responsibility to handle requests and automatically distribute data between nodes, in some sort of high-availability backup.
The advantages of NoSQL systems
NoSQL databases, in contrast with relational databases (such as older versions of MySQL and PostgreSQL), shine when the amount of data becomes too big, and also when we don't need the Features of relational databases (such as triggers or stored procedures).
Before we continue, let's...