Custom API Development Services

Would you like to power up your mobile app or eCommerce store with custom API integration? We provide custom API development services for any business purpose.

What API Means

API stands for Application Programming Interface while “application” here means a piece of software with a specific function and “interface” means rules and standards of connection between two applications.

When specialists provide an API development service, they set up a smooth process of communication through requests and responses. In a nutshell, to develop API services means to enable one app to get features from 3rd⁠-⁠party apps.

Case Studies

We analyze the client’s business processes and goals before starting application programming interface development. This way, we can choose the appropriate solution or develop a custom API.

Identity Verification Services Development: Swordfish

Identity Verification Services Development: Swordfish

We built a set of top-market identity verification service apps that fully automated contacts data gathering and management, making it a 1-minute procedure.

Parking App Development Case Study

Parking App Development Case Study

A car parking app development study: Fively created a booking app for businesses that solved the parking problem at the Scandinavian airports.

A Shopify Case Study. Abandoned Cart Recovery Solution: MessageBuy

A Shopify Case Study. Abandoned Cart Recovery Solution: MessageBuy

A Shopify case study on abandoned cart recovery solution development with personalized SMS notification, that increased consumers' conversion by 40%.

Financial Management Accounting System Development

Financial Management Accounting System Development

A developed from a scratch financial management accounting system that automated the business owners’ workflow by 70% and helped CEOs make data-driven strategic decisions.

CRM Customization and Configuration: Volt

CRM Customization and Configuration: Volt

We have provided our CRM customization services to the company, that electrifies dozens of widely-known music festivals all across Europe.

API Development Services

We are an API integration company. Our developers can integrate custom API to extend your application’s functionality by connecting it with third-party services and devices.


API consulting

You share your business needs with us, and we tell you which type of Application Programming Interface development is best to achieve your goals.


API architecture designing

We analyze your business processes and select the right architecture before we develop API features.


Custom API development

We provide custom development to ensure the best performance and ROI for your product.


Full⁠-⁠cycle API testing

We provide all types of API testing and a full⁠-⁠cycle quality assurance procedure for your application.


API integration

We work with payment gateways, Magento custom API development, Shopify customer API, web APIs, etc.


API maintenance and support

We offer long⁠-⁠term support and maintenance connected to our API development services.

Third⁠-⁠Party API Integration Services

Third⁠-⁠party API integrations mean taking features and data from various providers. We offer custom API development enabling any functionality that your website, eCommerce store, or mobile app needs to have – from payment support to social sharing.

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Payment gateways APIs

We help you handle payments quickly and securely, providing custom API integration with wide⁠-⁠spread payment gateways like Stripe, PayPal, and PayU.


SMS communication APIs

We upgrade your communication capabilities using seamless web service API integration with popular cloud platforms like Twilio, Nexmo, and Plivo.


Shipping carriers APIs

We offer bespoke application program interfaces integration with leading shipping carriers like fedEX, USPS, and UPS.


Social metworks APIs

We offer API integration services to connect platforms like Facebook, YouTube, and Instagram with your website, analytics system, or eCommerce store.

Are you planning an API development project or just need API integration services?

Our experienced developers can accurately calculate the cost of such a project for you.

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Process Flow

A custom application programming interface development is a project that consists of several integral steps.


Discovery and architecture

API development services always include a discovery phase to analyze your goals and choose the architecture.


Development and integration

We provide API development and custom integration into storage systems with files and data.


Quality assurance

Full⁠⁠-⁠⁠cycle and thorough API testing is a critical part of development and integration



During the deployment stage, we prepare API documentation to help you use new APIs more effectively.

How Does API Integration Impact Customer Experience Onboarding?

The key to top-tier customer onboarding is doing it quickly, accurately, and in compliance with regulations via the right software solution.

In the age of big data, you can integrate bespoke API to collect data from multiple sources using API development services from a professional API integration company.

Awards and Recognition

Fively is a custom software development company, that has been gaining recognition throughout its existence.


What Our Clients Say

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Frequently Asked Questions

Is API the same as integration?

Yes and no. Integration is a concept while API solution is the modern, cloud-based implementation of this concept. Legacy technologies of the 1990s and 2000s included manual coding to connect computers point-to-point, but modern web APIs are based on cloud computing. Today, bespoke API development is essential for integration projects.

What is API development and integration?

API development is converting the company’s business requirements into an API solution to enable connection with payment gateways, social networks, cloud services, and other applications to exchange data and bring new opportunities. Custom API integration services power up businesses across various industries enhancing productivity, customer relationships, and overall revenue.

Can we use an API in a mobile app?

Yes, we can. Mobile apps use APIs just like web apps do. These are the most common API used in native mobile applications: Google Maps API, Facebook API, AccuWeather API, and so on.

What programming language do you need to write an API?

Developers use a wide selection of programming languages to build custom API solutions. For example: .NET, Python, Java, PHP, JavaScript, С++, and Ruby.

Can you create an API in Python?

Python development is a very popular choice for custom API integration. This programming language is versatile and robust, allowing you to create user-friendly features and solve lots of challenges in the process of development.

What are the API development services?

Services include business analysis, the choice of architecture, API development, API testing, custom API integration, and continuous support. We provide full-cycle development and integration for businesses of all sizes.

What are the 4 types of API?

There are public (open, external) APIs, private (internal) APIs, partner APIs, and composite APIs.

What are public APIs?

Public APIs are also called open or external. Their main characteristic is being available for any development team to use. Therefore, public APIs have public API documentation, do not require specific authorization and security measures, and only share limited chunks of information.

Are public APIs always free?

Many of the public APIs are free of charge. Some other opportunities for application program interfaces integration may be subscription-based for commercial use. Payments usually depend on the number of requests.

What are partner APIs?

Partner APIs are shared between business partners. There is quite a strong level of authorization and security for specialists that provide a partner API development service.

What are private APIs?

Private, or internal, APIs are intended only for the in-house use by the business that asked for custom API development. The purpose of internal APIs is exchanging data smoothly between various applications and teams. The only developers that can have access to private APIs and API documentation are those working for this company.

What are сomposite APIs?

Composite web APIs differ from other types, because they are not about access to data. Composite APIs, as the name suggests, can combine several APIs to make a bundle request to more than one server at once. As a result of composite API integration, developers can get a unified response with various data collected from multiple sources.

How do you use a composite API?

Composite APIs decrease the number of requests and therefore reduce server load, making all systems work faster. Composite web APIs are essential when you build a software solution that has microservice architecture. In addition, an API developer can use an application programming interface to fully automate the chain of requests-responses.

What is an example of API development?

API integration services play a critical role in the eCommerce industry. For example, Magento 2 custom API development. Creating an order from a shopping cart is a simple action for a user, but it needs several requests to a server. This is when developers apply a composite API: creating a customer profile, making a new order, adding an item, then maybe adding one more item, and finally, changing the status. All of it works the same if you use a composite Shopify customer API. If you are interested in Shopify app development, we have just the right expertise.

How does an API work for business?

The best way to explain is to give real-life examples. Take Waze, a traffic app – it communicates with municipal service APIs to get information about accidents, road repairs and closures, service vehicles, etc. In addition, the app gathers data about city traffic. As a result, Waze helps to navigate through the streets and attracts more tourists.

How does API integration impact customer experience: onboarding, user-friendliness, and management?

API integration services can help you provide a superb user experience and make onboarding easier for new customers. API solutions can upgrade web and mobile apps or IoT devices. How does it work? You can create APIs to automate processes using native formats for each platform. This way, customers interact with user interfaces that feel convenient and familiar. In addition, API integration can reduce response time when customers upload their data. By exchanging important business-related information between your systems, you make digital experiences more user-friendly, adding up to customer satisfaction.

What is the price of API development services?

The price depends on the number of factors. Do you use a public or private API? How many 3rd-party apps do you wish to connect? If you build a simple MVP, the pricing will be quite affordable. The more complex functionality your project requires, the higher the final price is. Another factor is the location of the development team. These days, it is often easier for a business to choose an API integration company from Eastern Europe than to hire specialists from countries with higher prices for custom API development. If you need a professional estimation of your API project, get in touch with our team for a free consultation.

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