Which NoSQL storage to choose

Question

According to Wikipedia NoSQL article, there are a lot of NoSQL implementations.

What's the difference between document-oriented and key-value storages (as people mention them most often)?

Answer 1

Here's a blog post I wrote, Visual Guide to NoSQL Systems, that illustrates the major differences between some of the most popular systems. The biggest difference between them is which of the following two they choose to optimize for: consistency, availability, and partition tolerance.

Answer 2

At one level document and key/value are quite similar - both will return an object when you request a key. In pure key/value that object will be a simple string, although it can be a serialized complex object. A document database extends this with functions to work with this object such as partial update functionality or search indexing.

Beyond that you will need to think about your specific requirements - NOSQL covers a lot of different systems, and unlike SQL databases they all have quite different advantages/disadvantages for a specific scenario.