In this section, we are going to learn about NoSQL databases. Really? NoSQL? Are we not going to use a database to store our critical data? Of course we are going to use a database to store our data; however, it won't be a traditional relational database, which has a strict predefined schema and columns that have a standard data type. With NoSQL databases, everything is document-oriented and we can store data in one place without worrying about the data types. NoSQL databases hold collections of documents.

We can still perform database activities such as the following:

• Creating a document
• Inserting a document
• Editing an existing document
• Deleting a document

We can also perform a lot of advanced functionality, such as indexing and authentication. There are a lot of open source as well as commercial solutions that provide NoSQL databases. Here's a quick list of some of the NoSQL database providers:

• MongoDB
• Redis
• RavenDB
• Firestore
• MemcacheDB

During the course of developing our application in this chapter, we will implement Firestore as our backend system. In the next section, we will learn about some of the important tasks we will undertake involving these databases.