NoSQL Databases

• flexible schema, add or remove columns with ease
• great for sparse data
• horizontally scalable
• not ACID compliant
• can store any type of data in one place
• great when transactional data is not important, but ease of fetching complex data structures is required

Types

1. Key-value stores
   1. great for fetching key-value pairs efficiently -
      • caching
   2. Dynamo, Redis, …
2. Document databases
   1. documents with different structures grouped into collections
   2. MongoDB, CouchDB, …
3. Wide-Column databases 2. Casandra, HBase, …
4. Graph databases
   1. entities are nodes with properties, edges connect entities based on relationships
   2. Neo4J, InfiniteGraph, …