Meteor uses MongoDB on the server side, and a version of MongoDB, Minimongo, on the client side. It's capable of using any other NoSQL/document-oriented database, but MongoDB comes by default with the Meteor installation. This feature makes your programs much simpler and easier to write and works really well for quick, lightweight data storage.
Traditionally, most data is stored using a relational model. The relational model, with all of its associated rules, relations, logic, and syntax, is an integral and invaluable part of modern computing. The rigid structure of a relational database, with exact requirements for each record, relation, and association, provides us with quick searches, scalability, and the potential for deep analytics.
This type of exactness, however, isn't always necessary. In the case of our Lending Library app, for example, a full-fledged relational database would be overkill. In fact, in some cases, it's more...