MongoDB is a flexible and scalable NoSQL database. It's non-relational, maintaining its records as documents in collections as opposed to rows in tables. MongoDB is schemaless; its collections are flexible and do not enforce a particular data structure.
MongoDB documents are stored as binary encoded JSON, or BSON. The object-oriented nature of its documents makes MongoDB well suited for use with object-oriented languages such as JavaScript.
As with all databases, MongoDB offers CRUD operations. Operations on MongoDB are carried out using JavaScript-like syntax.
Optimizing MongoDB performance as a developer involves reducing the amount of data returned by queries and using indexes well.
In the next chapter, you will begin handling web requests for your SPA using the Express web application framework.