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Comprehensive Guide to API Development: Building Modern APIs

Isla Sibanda
May 14, 2024 | 15 min read
Microservice Orchestration

It’s no secret that software applications rarely operate in isolation. They need to communicate and exchange data with other applications, platforms, and services to provide users with rich and seamless experiences. This is where APIs (Application Programming Interfaces) come into play.

APIs have become the backbone of modern software development, essential for web applications and every software developer. They allow developers to build applications more efficiently by leveraging existing services and data sources. In fact, data shows that nearly 90% of developers are using APIs in some capacity.

API development promotes modularity, reusability, and innovation, allowing companies to create robust ecosystems around their products and services.

What is an API?

API is a set of rules and protocols that allows different software applications to communicate and interact with each other.

It defines methods and data formats that a program can use to perform tasks such as reading and writing data or requesting services from another application.

APIs are often used to enable integration between different systems, such as allowing a website to access data from a database or a mobile app to communicate with a server. Likewise, modern-day APIs can have a plethora of functions, such as improving cloud cost management, giving access to AI models, or just plain old connecting multiple apps so they work in unison.

Understanding How APIs Work

APIs work by allowing a client application to send an API request to a server through an API gateway, which then processes the request and sends a response back to the client.

The request is made using a specific protocol, such as HTTP, and includes information about the operation the client wants to perform, such as retrieving data or updating a resource.

How an API typically works:

  • Step 1: API Request. The client application sends a request to the API, asking for specific data or requesting a particular action to be performed. This request follows a predefined format and structure specified by the API.
  • Step 2: API Receives Request. The API endpoint receives the request, verifying the API key and ensuring that the request follows the correct protocols. Depending on the API's security requirements, it may need to authenticate and authorize the client application before processing the request.
  • Step 3: Processing the request. Once authenticated and authorized, the API processes the request. This may involve querying a database, performing calculations, or interacting with other systems or services.
  • Step 4: API response. After processing the request, the API prepares a response. This response contains the data or the result of the requested action, formatted according to the API's specifications.
  • Step 5: Client receives response. The client application receives the response from the API. It can then process and use the data or functionality provided by the API to update its user interface, perform additional operations, or fulfill the user's request.

4 Types of APIs

API development comes in several types, each designed to cater to specific needs and usage scenarios in software development.


REST APIs, also known as RESTful APIs, follow a set of principles and constraints for designing web services and are a key component in API integration across platforms. They use HTTP methods (GET, POST, PUT, DELETE) to perform operations on resources identified by URLs.

REST APIs are widely used for building web-based applications and mobile apps, as they provide a lightweight and efficient way for different systems to communicate over the internet.

Developers love them for their simplicity, scalability, and compatibility with web standards. This makes them useful in things such as the proliferation of green hosting, where they can manage data centers more effectively and reduce their carbon footprint.

They are also used in:

  • Mobile Apps
  • Internet of Things (IoT)
  • Integrations
  • Public APIs
  • Cloud Services
  • Content Management Systems
  • Financial Services (Banking, Payments, etc.)
  • Internet of Vehicles (IoV) and Automotive Systems

Key Characteristics of REST APIs

  • Stateless. , meaning that each request contains all the necessary information to complete the request. The server does not maintain any client context between requests, making the API more scalable and easier to manage.
  • Client-Server. REST APIs follow a client-server architecture, where the client (e.g., a web or mobile application) and the server (e.g., a web service) are separate entities that communicate through a standardized interface.
  • Cacheable. REST APIs can be cacheable, allowing clients to store responses and reuse them for subsequent requests. This can improve performance and reduce the number of requests to the server.
  • Layered System. REST APIs can be designed as a layered system, where each layer provides a specific functionality or service. This allows for better scalability, security, and flexibility.

For more on REST APIs, check out this


SOAP (Simple Object Access Protocol) APIs are and use a more rigid and structured approach to communication. They define a formal contract (WSDL) that specifies the available operations and data formats. SOAP APIs are often used in enterprise environments and can provide advanced features like transaction management and security.

Other uses include:

  • Web services
  • Financial services
  • Telecommunications
  • B2B integration

Key Characteristics of SOAP APIs

  • Protocol-based. SOAP APIs follow a strict protocol that defines how data should be formatted, exchanged, and processed. This protocol is defined by the SOAP specification, which is an industry standard.
  • XML-based. SOAP APIs use XML for encoding data and defining the structure of the messages exchanged between the client and the server. This makes SOAP messages more verbose and larger in size compared to other data formats like JSON.
  • Platform-independent. SOAP APIs are designed to be platform-independent, meaning they can be used to facilitate communication between applications running on different operating systems, programming languages, and hardware platforms.
  • Rigid structure. SOAP APIs have a more rigid structure and predefined set of rules that must be followed for the communication to be successful. This structure includes elements like envelope, header, body, and fault.

3. GraphQL APIs

GraphQL is a query language and runtime for APIs that allows clients to request and receive only the data they need. It provides a flexible and efficient way to retrieve and manipulate data from multiple sources through a single endpoint.

The most common GraphQL API uses include:

  • Complex data requirements:
  • Single-page applications (SPAs)
  • Mobile applications
  • Third-party integrations

Key Characteristics of GraphQL APIs

  • Query language. GraphQL APIs use a query language that allows clients to specify the data they need. This provides a flexible and efficient way to retrieve and manipulate data.
  • Single endpoint. GraphQL APIs provide a single endpoint that can handle multiple queries and operations. This simplifies API design and makes it easier for developers to use.
  • Hierarchical data fetching. GraphQL APIs can fetch related data in a single request, reducing the need for multiple round trips to the server. This is achieved through hierarchical data fetching, where clients can specify the nested data they require.
  • Real-time updates. GraphQL APIs can leverage technologies like WebSockets to enable real-time updates and subscriptions, allowing clients to receive data updates automatically without having to poll the server.

4. WebSocket APIs

WebSocket APIs enable real-time, bidirectional communication between a client and a server over a single, long-lived connection. They are commonly used for applications that require real-time updates, such as chat applications, online games, or stock tickers.

Other popular uses include:

  • Internet of Things (IoT)
  • Streaming services
  • Real-time analytics
  • Multiplayer games

Key Characteristics of GraphQL APIs

  • Full-duplex communication. WebSocket APIs allow for full-duplex communication, meaning that both the client and the server can send and receive data simultaneously over a single, persistent connection.
  • Real-time data transfer. Unlike traditional HTTP requests, which are stateless and require a new connection for each request, WebSocket connections remain open, allowing for real-time data transfer without the need for constant requests and responses.
  • Low overhead. WebSocket APIs have a lower overhead compared to traditional HTTP-based APIs, as they use a more efficient binary protocol and avoid the overhead of establishing new connections for each request.
  • Cross-platform compatibility. WebSocket APIs are supported by most modern web browsers and can also be used in mobile apps, desktop applications, and server-side environments, making them highly compatible across different platforms.

Key Components of API Development

api development ambassador

API development involves several key components that are essential for designing, developing, and using APIs effectively.

  1. API specification. Defining the structure, endpoints, methods, request/response formats, and data models of your API. This serves as the contract between the API provider and consumers.
  2. Authentication and authorization. Implementing secure access controls, such as API keys, access tokens, OAuth, or JWT (JSON Web Tokens), to ensure only authorized clients can access the API resources.
  3. API documentation. Creating clear and comprehensive documentation that explains the API's functionality, endpoints, request/response formats, authentication methods, and any required parameters or headers.
  4. API testing. Thoroughly testing the API endpoints, validating request/response formats, ensuring proper error handling, and checking for edge cases and potential security vulnerabilities before releasing the API.
  5. API security. Implementing proper security measures to protect the API from threats like unauthorized access, data breaches, and denial-of-service attacks, such as using HTTPS, input validation, rate limiting, and following security best practices.

What are the Steps in the API process?

The API development process typically involves several steps to ensure the creation of a reliable, secure, and well-documented API. Here’s a simplified overview of the typical API development process:

1. Planning

The first step in API development is to define the goals and intended users of the API. This involves understanding the needs of developers who will use the API and designing the API to meet those needs.

It is important to consider both functional and non-functional requirements, such as performance, reliability, and security.

2. API Design

The API design process involves creating an architecture that fits the requirements and reflects the needs of developers.

This includes defining the API's endpoints, methods, parameters, and data formats. It is important to ensure the API is usable, reliable, scalable, and secure.

3. API Development

Once the API design is complete, the next step is to develop the API. This involves writing the code that implements the API's functionality and integrates with other systems or services.

It is important to use best practices for API development, such as using throttling, allowing overriding HTTP methods, and making proper documentation.

4. API Testing

After the API is developed, it is important to test it thoroughly to ensure that it meets the requirements and functions as expected.

This involves testing the API's endpoints, methods, parameters, and data formats, as well as testing its performance, reliability, and security.

5. Monitoring

Once the API is deployed, it is important to monitor its success metrics, such as uptime, requests per month, monthly unique users, response times, server CPU/memory usage, and time to first profitable app.

It is also important to collect user feedback and incorporate changes into the next iterations of the API.

API Development Must-Have Features and Best Practices

Must-Have Features API DevelopmentWhen developing APIs, it's crucial to follow certain must-have features and best practices to ensure a high-quality, secure, and user-friendly API. These essential features should be included in any API you create:

  • Consistency in naming conventions and response formats
  • Reliability under heavy load
  • Security against common API development vulnerabilities
  • Accessibility through secure authentication and authorization mechanisms
  • Flexibility throughout the API's lifecycle
  • Extensibility, so changes don't break your API

Best Practices in API Development

Here are some of the best practices developers can use to create efficient, scalable, secure, and user-friendly REST APIs that meet the needs of modern software development:

  • Use clear and consistent naming conventions for endpoints to improve API design and developer experience, and prevent confusion or errors.
  • Use the correct HTTP methods (GET, POST, PUT, DELETE) for CRUD operations to ensure efficient and secure API communication.
  • Design APIs that adhere to best practices for creating robust, scalable, and secure software systems.
  • Implement robust authentication and authorization strategies to protect APIs against threats and ensure data integrity.
  • Implement security measures, including data encryption and SSL/TLS, to protect APIs against threats and ensure data integrity.


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