If you’ve built an application that stores its data in a relational database like MySQL or PostgreSQL, then you’ve likely run into situations where joining two or more large tables becomes very slow and painful. Because our SQL Layer stores its underlying data in our Key-Value Store, it has a unique feature called “Table Groups” that alleviates painful joins and allows your application to stay speedy.
NoSQL. Next Generation Databases mostly addressing some of the points: being non-relational, distributed, open-source and horizontally scalable. Wide Column Store: Hadoop / HBase, Cassandra, Hypertable, Document Store: MongoDB, Elasticsearch