In our discussion of NoSQL types and databases, we will primarily focus on the following characteristics of NoSQL databases:

• In-memory databases
• Columnar databases
• Document-oriented databases
• Key-value databases
• Graph databases
• Other NoSQL types and summary

Most types of NoSQL used in the industry today fall into one or more of these categories. The next few sections will discuss the high-level properties of each of these NoSQL offerings, their main advantages, and products in the market that fall into the respective categories.