We will first spend some time explaining the basic steps to designing a system. My suggestion is as follows: "Design is the first stage of any successful system, and encompasses everything that you work on before you begin implementation." In this section, we will focus on the general principles and core aspects of each element of the system.

Two main core elements should be at the forefront when designing each part of the system: The interface, or how an element of the system connects to the rest, and data storage, how this element stores information that can be retrieved later.

Both are critical. The interface defines what the system is and its functionality from the point of view of any user. A well-designed interface hides the implementation details and provides some abstractions that allow for a consistent and comprehensive way of performing actions.

The heart of virtually every successful working system is the data. This is where the value of the system lies. Any seasoned engineer will tell you that an organization can reconstruct a system when the data is available, even if the code that produced it is lost, rather than recover from a total loss of the data, even if the application code is available.

The storage of data is, then, the core of the system. There are many options we can choose from when it comes to storing our data. What kind of database? Store the data in one data storage facility, or several? The traditional way of using raw access to the database, typically in plain SQL statements, is not the most efficient option, and it's prone to problems when complex systems are involved. Other kinds of databases exist that don't even use SQL. We will look at multiple options along with their pros and cons.

Changing how the data is stored in the system is hard once the system is in operation. It isn't impossible but will require a lot of work. The storage option is arguably the founding stone when designing a new system, so be sure that the chosen option fits your requirements. It can be difficult to design something that isn't overly complex but also allows the allocated space to grow as the application starts to store more and more data as it's used.

This section of the book comprises the following chapters:

1. API Design, describing how to create useful, yet flexible, interfaces
2. Data Modeling, with different ways of handling and representing data to ensure that this critical aspect is well thought through from the outset