If you work in the tech industry or are a technology freak then you must have come across the term “API”. Today, API plays a bigger role in the economy than it did ever before. API are everywhere and we use it daily. From booking tickets, logging on Facebook, to making payments via PayPal, we use API for many times in our daily life.

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Apart from that, there are also fun APIs such as Fun Translations which translates English to languages like Dothraki, Minion, and Klingon. Then there’s Pokémon API. which provides you with all the Pokémon data in one place.

The world of APIs is big and surely the one to be explored. And that’s exactly what I’ll be doing with you all through this article. In this article, we will discuss everything about APIs. So, without any further ado, let’s begin.

What is API?

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API (Application Programming Interface) is nothing but a set of instructions, requirements, and standards that enable an app or software to employ features or services of some other application, device, or platform to offer better services.

In technical terms, it’s a set of programming code which allows data transmission between one software product with the other. It also consists of terms of this data exchange.

Application programming interfaces have two components:

• Technical specification which describes the data exchange options between solutions that have specifications done in the form of data delivery protocols and request for processing.
• Software interface which is written to the specification which represents it.

In this, the software which needs the access information or functionality from software calls its API along with specifying the requirements as to how the functionality or the data should be provided. The other software simply returns the data functionality as requested by the former application. API also specifies the interface by which both these applications communicate.

Each API is implemented by function calls which are the language statements that are used to request software to perform particular services and actions. Functions calls are nothing but phrases which includes nouns and verbs. Function calls are also described in the API documentation.

APIs can serve several purposes. Usually, they can speed up or simplify software development. Developers use APIs to add functionality from other providers to the existing solutions. Furthermore, they can be also used to develop new applications by using third-party providers.

Types of API

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APIs can be categorized based on their release policies.

Private APIs

The interfaces of this application software are designed to improve services and solutions within the organization .Contractors as well as the in-house developers can use these APIs to build new systems.

In this scenario, the app’s interface remains available only for those people who are working with the API publisher even if the app is publically available. With a private strategy, the company can take full control of the API usage.

Partner APIs

Partner APIs are used for software integration between two parties. These are also openly promoted and are shared with those business partners that have signed the agreement with the publisher. A company can benefit from extra revenue streams by granting its partners with capability benefits and access to data.

Meanwhile, they can also monitor as to how exposed digital assets are used. Furthermore, they also ensure if the 3rd-party solutions which use their APIs offer decent user experience or not. They also ensure if they maintain corporate identity in their apps.

Public APIs

Public APIs are also referred to as external or developer-facing. These APIs are also available for third-party developers. Public API program enables you to increase brand awareness. Furthermore, it also allows you to receive extra income if properly executed.

Public APIs can be also classified into two categories – first is open and the other one is commercial.

As per the Open API, all its features are public and can be used without any restrictive terms and conditions. It also states that the description and related documentation of the API must be available. Furthermore, it also says that it should be a freely available test and create applications.

If we talk about commercial API users either pay the subscription fees or use APIs on a pay-as-you-go basis. Publishers also offer free trials which enable the users to evaluate APIs before they purchase the subscription.

Composite API

Composite APIs are known for combining different service and data APIs. They are made by combining existing API functions which can perform many tasks in a single call. This boosts the execution speed along with enhancing the performance of the listeners in the web interfaces.

How does it work?

To understand the working of the API, let’s take an example. Assume that you have opened an ABC website or app to book a flight. You filled the form by entering all the details such as departure, return date, flight, city, and other respective details.

As soon as you submit, a list of flights will appear with details like seat availability, timings, price, and many other details. But how did it happen? It’s because of the APIs.

To provide such accurate data, the platform sends the request to the website so that it can access the database and get all the relevant data through API. The website then responds with the data which was delivered via API to the platform.

Here, the API acts as an intermediate which streamlines the data sharing process. On the other hand, the airline website and flight booking platform act as the endpoints. When it comes to communicating the endpoints, then API namely works in two ways which are SOAP and REST.

Now, that we have understood the working of APIs, let’s have a look at the basic terminologies used in API development.

Terminologies associated with API development

If you’re looking for a custom API development, then you must know the below terminologies.

API Key

It’s a unique code which is passed in the computer programs for authenticating user, developer, or calling program.

Endpoint

Interaction touchpoints between server and API are called Endpoint.

JSON (JavaScript Object Notion is a data format) is a data format that is used for APIs to interchange data. This interchange of data can occur between a web application and a server or two applications.

GET

It’s a method which is used for requesting data from the server at a specified resource.

POST

It’s a method used for sending data to the API server to update or create a resource.

OAuth

It’s an open-standard authorization or authorization framework for APIs. It offers secure and restricted access to the end-users data which is to be used by the application or third-party websites without accessing their password.

Latency

The time taken by the API to process a request and respond is called Latency.

Rate-limiting

The process of controlling the rate of incoming as well as outgoing traffic is called rate-limiting. It’s also defined as the total number of requests that a user hits to the API.

API Throttling

API throttling refers to the process in which the usage of APIs by consumers is controlled for a specific duration.

Tools for API development

There are many tools available when it comes to API development. Some fo the most prominent tools and products that developers use for API development are as below:

Apigee

Apigee is an API development management tool by Google. This tool is helpful when a company is updating their legacy apps or facilitating data transfer between apps and services. Apart from that, it’s also useful when a developer is building connected apps.

Dredd

Dredd is an HTTP API testing framework. It is used to validate the description of an API in the backend. It also goes through API’s description thoroughly along with determining if the API is validated or not.

APIMatic

APIMatic is a developer experience platform for website APIs. Developers use it to generate SDKs for their APIs for 10 platforms. Furthermore, it’s also used to keep it in sync with the API updates.

This tool also enables the developers to convert API descriptions into multiple formats such as WADL, Swagger, RAML, OAI format, IO Docs, API Blueprint, HAR 1.4, Postman Collections, etc.

Sandbox

Sandbox offers a quick and easy mock RESTful API from API definitions. It also reduces the risk and cost associated with third-party API calling during testing.

Postman

Postman enables app developers to evaluate the performance of the API by documenting and testing it. It’s also an interactive tool that can be set up for automation.

SoapUI

SoapUI is an open-source testing tool. It can operate on cross-platforms. Furthermore, it can also automate both functional and non-functional tests. It is used for regression, compliance, executing, security, and load tests for the Web APIs.

Swagger

Swagger is an open-source framework that is used for API development. Big technology names such as GettyImages, Apigee, PayPal, and Microsoft use Swagger.

JMeter

JMeter is open-source software. It’s used in performance testing of RESTful API.

Must-have features in API design

Before you start building APIs, you must keep a few points in your mind. These points will act as a catalyst in your API development process and will also help your team to stay on the same page. Let’s have a look at these points one by one.

Authorization and Authentication

In simple words, Authentication means verifying the right identity. On the other hand, Authorization means to decide if the verified user is permitted to perform an action on a specific source. For example, John (an authenticated user) can get a resource; however, he’s not allowed to create a resource.

OAuth, OAuth2, and JWT are some of the most commonly used specifications for managing authorization and authentication.

Pagination

It’s obvious that with time your database will grow. And when that happens, then you’ll observe that some of the resources are taking a longer time than usual to retrieve. The most common way to approach this situation is by caching the objects or creating pagination.

Paging is nothing but a process to determine as to how much data should be displayed and at what frequency.

Sorting also ensures that the user receives the data as per the requirements, condition applied, and modifications.

These factors help in minimizing processing time, ensuring a high-level security, and a good response time.

Cache

By developing a Cache strategy, you can retrieve resources at a lightning speed. Once the data is ready for consumption in an in-memory database, then it will reduce the cost of your requests. You can use tools like Redis and Memcached for developing a Cache strategy.

Wrappers

API wrappers are containers or packages which are language-specific. They combine various sets of API calls into user-friendly functions. The wrapper also calls several API calls without interacting with the user.

HATEOAS

HATEOAS (Hypermedia as the Engine of Application State) is one of the modules of the REST application architecture. Here any content which consists of a link to other forms of media such as text, images, videos, etc. is called hypermedia.

HATEOS enables clients to interact with REST API with the help of responses which are provided by the server dynamically.

Error handling

An efficient error handling can make the debugging process easier as it identifies if the problem was a result of server or client error. For some errors, the client can change the request, whereas, for the others, they would require to contact support. Some of the helpful error handling methods are as follows:

• Use error codes with well-known standards
• Offering the right number of errors
• Describing the cause of the error
• Segregating domain and general errors.

Validation

Validation in APIs refers to the verification of correctness of data. Validation can be categorized into two types:

• Server validation
• Client-side validation

In client-side validation, prompt feedback is given, for an instance marking out the incorrect entry in red color, tooltip for correction, etc.

Server-side validation involves mundane tasks such as what kind of property it is (account number, email, etc), validating if the property is required, or if the property is not needed if another property is already there.

Testing

API testing is very similar to software testing. API testing includes testing the APIs directly as well as the part of integration testing to find out whether it meets the expectations for performance, functionality, security, and reliability. JMeter, Postman, and SoapUI are some of the most popular tools that are used for API testing.

Throttling

When it comes to redirecting the overflow of traffic, safeguarding from DoS (Denial of Service), and backup APIs, app throttling is the best practice which you all should consider.

Enable overriding HTTP method

There are some proxies, who only support POST and GET methods; this is why you must allow your RESTful API to override the HTTP method. You can do this by employing the custom HTTP Header X-HTTP-Method-Override.

SDK and Libraries

Offer important resources to the development team to boost the speed of services development and implementation. You can do this by offering resources that contain reusable processes and code.

Security

You must ensure that your API is secure but not at the cost of user-friendliness. If any user spends more than 5 minutes on authentication then it means that your API is far from being user-friendly. You can use token-based authentication to make your API secure.

Documentation

Offering a wide range of documentation is another great practice that you must consider. You must create extensive documentation for an API that enables other mobile app developers to understand the entire process in detail so that they can utilize that information to provide a top-notch user experience.

In a nutshell, well-crafted API documentation will decrease the project cost, implementation time, and enhance API efficiency.