Choosing NoSQL over RDBMS
The main advantage of NoSQL is horizontal scalability and distributed storage. That means you can have a large number of ‘cluster nodes’ and write to them in parallel. The cluster will ensure changes are propagated to the other cluster nodes eventually (eventual consistency).
The developer requires high coding velocity and great agility in the application building process. NoSQL databases have proven to be a better choice in that regard, using object-focused technologies such as JSON.
As a database grows in size or the number of users multiplies, many RDBMS-based sites suffer serious performance issues. If organization is facing such issues, then consider using NoSQL technologies.
Data warehousing & analytics
Real time analytics for operational data is better suited to a NoSQL setting. Where data is brought together from many upstream systems to build an application, NoSQL is a must.