In modern development, the API is some sort of intermediary for different programs to communicate with one another. Companies like Celadonsoft are doing the API Development to facilitate integration, increase product flexibility and accelerate development roadmap.

Why Is an API Important?

APIs become an integral part of the software ecosystem because:

• Automate processes – systems can interact without manual intervention.
• Extend functionality – allow integrating third-party services (for example, payment gateways or analytical tools).
• Provide scalability – developers can scale applications without the need to radically change the architecture.

Basic API Types

During the process of API Development, one has to understand its types, because the choice of the concept launch influences performance, convenience, and security:

REST API

• The most popular approach by using HTTP and REST.
• Simple architecture; easy to scale.
• Use JSON or XML to represent data in transit.

GraphQL API

• Flexible tool that allows the client to demand only those types of data that it needs.
• More effective in complex projects with a huge volume of data.

SOAP API

• Corporate solutions that have high security requirements.
• Based on XML, it involves complex processing. 

gRPC 

High-performance API protocol running over HTTP/2, used for microservice architecture and cloud solutions.

Which API to Choose?

The choice of API depends on specific tasks:

1. For web applications – REST or GraphQL.
2. For complex corporate solutions – SOAP.
3. For microservices and high data transmission speed – gRPC.

API is the foundation of interaction between services. It is important not only to select the right type, but also to design it correctly, taking into account user needs and scalability of the system. In the following sections, we will cover the key stages of API development – from the concept to launch.

Planning and Requirements Definition

Before you start developing an API, it is essential to clearly define its objectives, audience and functional requirements. This step lays the foundation for an efficient and convenient API, minimizing risks and simplifying further API development.

Defining the API’s Goals

Foremost, the key questions need to be answered:

1. What task should the API solve?
2. What services or applications will use it?
3. What key functions should the API provide?

Defining goals allows you to avoid unnecessary complexity and focus on creating functionality that is really needed.

Identification of the Target Audience

The API can be used by different groups of users:

• Internal developers – for integration within the company.
• Third-party developers – to create new services and products.
• Partner companies like Celadonsoft – to interact with your business.

Understanding the audience helps to choose the optimal architecture, authorization mechanisms and level of detail documentation.

Definition of Functional Requirements

Clearly defined functional requirements simplify the development and testing process. These include:

• List of endpoints and their tasks.
• Supported HTTP methods (GET, POST, PUT, DELETE).
• Query and response formats (JSON, XML).
• Request processing speed requirements.

Determination of Non-functional Requirements

In addition to functionality, it is important to consider non-functional parameters such as:

1. Security – what authentication and authorization mechanisms will be used?
2. Scalability – will the API handle load growth?
3. Reliability – how will the API handle system failures?
4. Compatibility – Do you need to support old versions of the API?

Design API: Best practices

Coding the API is a key step that determines its ease of use, its scalability and future support. At this stage it is important to build the right architecture, define the structure of endpoints and consider potential use scenarios.

Development of a Resource-Oriented Architecture

The API should be built around clearly defined resources. For example, if your service manages users and orders, it makes sense to present them as separate resources:

• GET /users – get list of users
• POST /users – Create new user
• GET /orders – get order list
• POST /orders – create new order

Following the principles of REST or GraphQL helps to create a predictable, logical and user-friendly API.

Defining HTTP Endpoints and Methods

Choosing the right HTTP methods is the basis for proper API interaction with clients. Use:

• GET – for data retrieval
• POST – to create a new resource
• PUT/PATCH – to update an existing resource
• DELETE – to delete a resource

It is influential to keep the URL structure logical and avoid excessive endpoints.

API Version Management

API is evolving, and changes are inevitable over time. To avoid integration failures, it is important to properly manage the API versions:

• Use versioning in URL: GET /v1/users
• Or send the version via Accept headers: application/vnd.company.v1+json
• Ensure backwards compatibility when changing

Multiple version API support allows customers to seamlessly migrate to new versions without critical crashes.

Data Format and Standardization of Responses

Define a common data format that the API will return. Most commonly used:

• JSON is the de facto standard for REST API
• GraphQL – convenient for flexible queries with selection of the required data
• XML – Common, but rarely used in modern APIs

This makes it easier to handle API responses on the client side.

User Identification and Security

In the design phase it is important to define how the API will identify and authenticate users:

• Use OAuth 2.0 or JWT for secure authentication
• Restrict access to data via API keys or tokens
• Implementation of CORS and protection against CSRF-attacks for web applications

Without a well-designed API authentication, the API remains vulnerable to attacks and data leaks.

Good API design – the key to its convenience, security, and scalability. By defining architecture, methods and versioning at an early stage, many problems can be avoided in the future. It is important to strive for a logical structure, ease of use and predictability of the API for developers working with it.

Implementation and Selection of Technology

API development requires the selection of the appropriate stack of technologies that will provide reliability, performance, and friendliness regarding further maintenance.

Stack Selection

During API development, scalability, compatibility, and performance are factors that need to receive critical consideration. The major component of the stack of technology includes:

• The Programming Language: most popular solutions include JavaScript (Node.js), Python (FastAPI, Flask, Django), Go, Java (Spring Boot), and C# (.NET). 
• Frameworks and Libraries: they speed up the development and give standardization. Examples include Express.js, NestJS, FastAPI, Spring Boot, and ASP.NET Core. 
• Database: relational (PostgreSQL, MySQL) or NoSQL (MongoDB, Firebase, Redis) depending on project requirements. 
• Cache System: Redis, Memcached for optimization at API response level.

Implementation of Endpoints

Development of API – to define logic of processing of HTTP-requests and data structure. Besides, the following principles need to be adhered to: 

• RESTful architecture: the use of standard HTTP methods GET, POST, PUT, and DELETE. 
• For complex requests, consider using GraphQL-if clients want to have a bit more flexibility in requests, then GraphQL would be a very nice alternative to REST. 
• Explicit URL structure /users/{id}, /products/{id}/reviews: Logically organized resources.
• Support for pagination, filtering, and sorting – for working with big volumes of data.

Database and Integration with External Services

The API should interact well with the database as well as external services. 

This could include:

• An ORM/ODM for dealing with a database (Sequelize, TypeORM, Prisma (SQL), Mongoose (MongoDB)).
• Optimization of queries – making use of indexes, taking care to keep the number of queries down.
• External APIs – asynchronous calls, error reports, time-out processing.

API Security

API security is highly critical, especially when the system deals with confidential data or executes transactions of any sort.

Authentication and Authorization

It is important to use reliable ways of controlling the access to an API. Those include:

• OAuth 2.0/ OpenID Connect as a standard to provide secure authentication.
• JSON Web Token (JWT) – an extremely popular format of user data transfer.
• API keys are an elementary level to protect against and identify API clients.
• Basic/ Bearer Token Authentication – used in simple scripts.

Protection Against Widespread Attacks

It’s obvious that the API is exposed to many types of attack, so it’s necessary to apply:

• Protection against SQL injection-use of parameterized queries and ORM.
• CORS – Cross-Origin Resource Sharing-setting access policy between different domains
• Rate Limiting – limiting number of requests from one client-for example with Redis.
• CSRF Protection: Protection against Cross-Site Request Forgery by using CSRF tokens in forms and requests.

Access Restriction and Encryption

• Roles and access rights: Delineation of access to different API resources.
• SSL/TLS is a must-have encryption of traffic.
• Secrets storage: secure storage of API keys, passwords, and confidential data.

Testing and debugging

Before the API is deployed in the live version, a thorough testing and debugging process must be performed.

API Testing Methods

There are several levels of testing:

• Modular testing – checking of individual API functions (Jest, Mocha, Pytest).
• Integration testing – testing the API’s interaction with databases and other services.
• Load testing – performance testing under high loads (Apache JMeter, k6).
• Security testing – API vulnerability analysis (OWASP ZAP, Burp Suite).

Tools for Automated Testing

• Postman/ Newman – manual and automated API testing.
• Swagger/ OpenAPI – autogeneration of tests according to API specification.
• CI/CD-Test Plugin – automatic testing every time the code is updated.

Monitoring and Logging

• Centralized log collection – using ELK Stack (Elasticsearch, Logstash, Kibana), Grafana, Loki.
• Error monitoring and performance – Sentry, Prometheus, Datadog.
• Health Checks are the/health endpoints for API health checking.

Conclusion

\Creating an API is not just code development, but a complete process that includes design, implementation, testing, deployment and support.

Key findings:

• Well-designed API makes integration easier and reduces the number of problems.
• API security is a priority: attack protection and reliable authentication are critical.
• The quality documentation and SDK make the API user-friendly.
• Monitoring and logging help to react quickly to failures and maintain stability.
• Versioning and update strategy allow API to evolve without negatively affecting users.

If you are developing an API that is high-load and active, a well-thought-out architecture, reliable infrastructure and user support will be the key to its success.