Overview:
NoSQL (Not only SQL) have been growing beside RDB. The reason for growing is it’s good for Big Data.

Compare to traditional RDB, NoSQL is FAST for a large amount of data. RDB (Relational Database) support Transaction (Commit/Rollback) sometimes know as ACID (Atomicity, Consistency, Isolation, Durability). This is one of reasons that RDB is slow compared to NoSQL.

For example, NoSQL updates a data based on its last request; It’s like LIFO (Last In First Out). It has time stamp to determined the latest record.