The Birth of NoSQL
Now, in the 2010s, NoSQL is the latest attempt to overthrow the relational model’s dominance. The name “NoSQL” is unfortunate, since it doesn’t actually refer to any particular technology—it was originally intended simply as a catchy Twitter hashtag for a meetup on open source, distributed, nonrelational databases in 2009 . Nevertheless, the term struck a nerve and quickly spread through the web startup community and beyond. A number of interesting database systems are now associated with the #NoSQL hashtag, and it has been retroactively reinterpreted as Not Only SQL .
There are several driving forces behind the adoption of NoSQL databases, including:
- • A need for greater scalability than relational databases can easily achieve, including very large datasets or very high write throughput
- • A widespread preference for free and open source software over commercial database products
- • Specialized query operations that are not well supported by the relational model
- • Frustration with the restrictiveness of relational schemas, and a desire for a more dynamic and expressive data model 
Different applications have different requirements, and the best choice of technology for one use case may well be different from the best choice for another use case. It therefore seems likely that in the foreseeable future, relational databases will continue to be used alongside a broad variety of nonrelational datastores—an idea that is sometimes called polyglot persistence .