Dmitriy N. Full-Stack Developer

What is a backend?

Let’s distinguish two types of mobile apps. The first type is the apps that don't send requests to a remote database, and the second type are those that do. The first group includes applications like timers, alarms, sticker sets, some games and photo editors. The second group includes applications that need to at least register users and store their nameы and phone numbers. It needs a separate place to store this data, and this place is called the server, or backend, and the mobile development of such an application is usually done with the help of a client-server architecture.

The client part (frontend) is the mobile application which shows the user interface and functions to achieve the user's goals. If we take the online store application as an example, we see that the user interacts with products, searches and filters, sends items to cart and makes a purchase through this app.

The server part (backend) is a computer with a program running on it to process data. Like a mobile app, this program is also a code, and it must be programmed too. An online store application cannot exist without a backend which is responsible for item data presentation, accounting, order creation and payment processing.

A good backend has:

Flexibility, allowing backend developers to add new features without problems or crutches and thereby evolve the application;

- scalability;

- active technical support, capable of giving a quick answer to a question, quickly fixing a bug, making the right change in the interest of the product.

Though the backend is not visible for the mobile apps users, it plays an immense role. It's a separate part of your product that needs to be invested in. And if you don't distinguish the backend as an independent product, it will depreciate to mere API documentation.

What is an API

An API (Application Programming Interface) is the part of the backend which acts as a communication language between the server and the client (the mobile application in our case). The API is used to represent server data in a format that is suitable for this communication.

When we say mobile application API we don't just mean data presentation format, we mean the application that takes the data, processes it, and returns it to the client in that format. When we say "writing an API," we mean programming the business logic, writing the document, and coming up with the formats themselves.

A good API is characterized by:

- adherence to general development principles,

- up to date and complete documentation,

- stability of the work,

- fast response to the client’s,

- versioning.

It happens that the business logic is well written, but the API on the contrary is written poorly. To design and program APIs it is important to have specific knowledge: to know standard approaches and best practices, to understand how mobile applications work, to know the needs of the users.