(NoSQL) databases belong to a group of Non-Relational Database Management Systems. These databases have no predefined schema for data stores. They are designed for large scale web systems. Popular types of NoSQL databases can be classified into four types;
- Key-Value stores E.g. Apache Cassandra
- Document stores E.g. CouchDB
- Wide column stores E.g. HBase
- Graph databases E.g. Neo4j