MongoDB: The Definitive Guide, 3rd Edition

Chapter 9. Application Design

This chapter covers designing applications to work effectively with MongoDB. It discusses:

• Schema design considerations

• Trade-offs when deciding whether to embed data or to reference it

• Tips for optimization

• Consistency considerations

• How to migrate schemas

• How to manage schemas

• When MongoDB isn’t a good choice of data store

Schema Design Considerations

A key aspect of data representation is the design of the schema, which is the way your data is represented in your documents. The best approach to this design is to represent the data the way your application wants to see it. Thus, unlike in relational databases, you first need to understand your queries and data access patterns before modeling your schema.

Here are the key aspects you need to consider when designing a schema:

Constraints

You need to understand any database or hardware limitations. You also need to consider a number of MongoDB’s specific aspects, such as the maximum document size of 16 MB, that full documents get read and written from disk, that an update rewrites the whole document, and that atomic updates are at the document level.

Access patterns of your queries and of your writes

You will need to identify and quantify the workload of your application and of the wider system. The workload encompasses both the reads and the writes in your application. Once you know when queries are running and how frequently, you can identify the most common queries. These are the queries you need to design your ...