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Application Programming Interface – API

An Application Programming Interface (API) is a set of rules and protocols that software applications use to communicate with each other. APIs allow different software systems to interact without knowing the details of each other’s implementation, thus effectively enabling them to work together.

An example could be an API for determining shipping costs with a logistics company like FedEx. The API could return the shipping costs if you provide the starting location, delivery location, package dimensions, weight, and requested shipping speed. Software applications can send those parameters to the API and receive the shipping cost as a response.

APIs are essential in modern software development, particularly in distributed systems, cloud computing, and mobile applications. They facilitate faster development by allowing programmers to use pre-existing functionality rather than building everything from scratch.

There are several types of APIs, including web APIs, operating system APIs, database APIs, and many more. Web APIs, also known as HTTP APIs or REST APIs, are often used to provide services over the Internet. 

Key Aspects of APIs 

An API call or request is the process by which one software program asks another software program to perform a task. The communication happens via a request message, which includes a request method (e.g., GET, POST) and may also include data or parameters necessary to complete the request.  

After receiving an API call, the targeted system will return a response. This response usually contains the result of the task that was requested, along with a status code that indicates whether the task was successful and any relevant error messages.  

API Endpoints and Documentation

An API endpoint is a specific route or URL where other software programs can access an API. Each endpoint corresponds to a particular function.  

Documentation is crucial for understanding how to use an API effectively. Good API documentation will describe the available endpoints and the structure of the requests, along with details about the responses and examples of requests and responses.  

API Keys, Rate Limiting, and Security

An API key is a passcode that identifies the calling program, its developer, or its user to the API service. API keys are used to track and control how the API is used to prevent abuse or overuse of the API.  

Once an API user has access, it may still be necessary for the API provider to use rate limiting as a technique for limiting network traffic. It limits how often a client can repeat a specific API call in a certain amount of time.  

For example, an API service may limit the API requests to 10,000 per day without special approval so that a run-away software process in a user’s program does not overload the API process and impact its availability.  

APIs also need to be secured to protect sensitive data and prevent unauthorized access. Standard security measures include API keys, OAuth (Open Authorization), and tokens for managing access control.  


Overall, APIs are crucial building blocks that allow different software applications to interact and create more complex services.

They’re like bridges connecting various software applications, allowing them to send and receive data and perform operations on each other’s behalf.

Introduction to the World of APIs – 7 mins

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