The following elements determine whether or not to create a Related doc or a Nested doc. A document store is a group of documents such as JSON , XML, etc. JSON is a lightweight doc, generally representing data components, objects, and arrays. Cassandra belongs to what’s known as the “columnar” household of databases. The storage abstraction in Cassandra is a column somewhat than a row. The idea here is to retailer all the info in a column physically together on the disk, minimizing search time.