4 min. read

What is an API Call and How Does it Work?

Application Programming Interfaces (APIs) have profoundly changed how developers write software and are the foundation of an entire API-based ecosystem. As a set of rules—or middleware—that prescribe how two pieces of software or hardware interact, APIs have become a critical part of the foundation of containerized and distributed environments, as well as cloud- and mobile-enabled development. An API call is the mechanism by which APIs “request” an action from another piece of software or hardware. Without an API call, the API sits dormant. But what is the nature of API calls (aka API requests), and how do they function?

APIs and API Calls are Critical to Modern Apps

APIs are existing resources that help developers drive cost-effective, efficient software lifecycles. Research published in Forbes found that organizations using APIs over four years realized 12.7% more market capital growth than companies that did not. Additionally, a 2022 survey revealed that 74% of developers were using APIs for internal applications, 49% were creating third-party APIs, and 44% were creating partner-facing APIs. At that time, 68% of software developers had expected to increase their API use.

An increasing reliance on APIs puts a greater focus on ensuring API calls function flawlessly and quickly. In fact, the average response time for an API call should be less than one second. A delay of one second causes erodes performance, and a four-second delay leads to a poor user experience. 

What is an API Call?

Since application programming interfaces are the mechanism by which one program interacts with another, API calls are the vehicle by which they interact, exchange information, and functionality. Because APIs are built in layers or with components, the API request acts as the retriever or intermediary. It’s similar to a translator who helps two people who don’t speak the same language understand each other and exchange thoughts.

API Calls Access Data and Functions to Create a Seamless Experience

An API call aims to deliver data and functionality components as part of one seamless experience. For example, when a user directs a browser to a URL or logs into most apps, an API call makes the request via a message sent to a server. 

And, while API calls may appear simple on the front end, each request may require large amounts of data to enable a complete and reliable exchange. One mobile application, for example, could have five, 15, or hundreds of APIs to complete all of its functions.

How Does an API Call Work?

There are four API call steps that carry out the complete request cycle. Step one is when the API makes the call via its Uniform Resource Identifier (URI). The URI should include a request verb and headers, and a request body if needed. Step two is when the API makes the call to an internal or external program for data or functionality. The third step is when the API receives a response from the source program. Lastly, 

the API call transmits the data or functionality to the program that made the initial request.

As part of step one, there are five types of API calls or requests: GET, POST, PUT, PATCH, AND DELETE. These are the request verb or action desired.

GET: The API requests information from a source.

POST: The API requests that a new piece of information be created.

PUT: The API requests that an update be made to a piece of existing information.

PATCH: The API requests that an update be made to a part of existing information.

DELETE: The API requests that a piece of existing information be deleted.

APIs are used in different environments (like public, private, internal, or external) and within different architectures (monolithic, microservices, or unified). However, all API calls use one of four protocols.  

API Call Protocols Define the Rules of Exchange

A protocol defines the rules that an API call must follow, specifying the accepted data types or commands that can be exchanged. The most common types of API call protocols are REST, SOAP, RPC, or event-driven.

REST: Representational State Transfer is a web services API that more than 70% of public APIs use. 

RESTful software gives access to data (or payloads) via uniform and predefined operations. 

SOAP: Simple Object Access Protocol is more complex than REST, requiring more details on how the call should be handled. SOAP runs by strict rules and advanced security, requiring greater bandwidth.

RPC: Remote Procedure Calls include XML-RPC (aka extensible markup language), XML-RPC, or JSON-RPC. This call format is older and simpler than SOAP. 

Event-driven: These API calls work best when information or updated data needs to be transmitted in near real-time. 

Depending on a DevOps team’s needs, the types of endpoints, and the software use case, the suitable API types, protocol, and setup can deliver a fast and high-performance API call and user experience.

Keeping APIs and API calls secure

Today, software relies on countless APIs and requests for data and functionality. Each API call carries with it a small amount of security risk. Ensuring that each server is properly configured, APIs are adequately managed, and endpoints are scanned can help defend against nefarious or illegitimate requests. A robust end-to-end API security strategy provides the background strength to deliver a seamless, high-quality user experience and security-strong software product. 

Modern Cloud-Native Security Starts with Panoptica

Cisco’s Emerging Technologies and Incubation (ET&I) team is paving the way with “DevOps-friendly” cloud-native security solutions that fundamentally simplify conventional offerings. Our Panoptica solution simplifies cloud-native application security, making it easy to embed into the software development lifecycle. Panoptica protects the full application stack from code to runtime by scanning for security vulnerabilities in the cloud infrastructure, microservices (Containers or Serverless), the software bill of materials, and the interconnecting APIs. And best of all, it integrates with the tools that your application development and SecOps teams are already using. Try Panoptica for free!