What Is Asynchronous Programming And When To Use It?

By Indeed Editorial Team

Published 17 July 2022

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

Computer programmers use a variety of concepts when building software, websites or applications. Asynchronous programming allows them to execute various tasks in parallel without having to wait for a task to be complete before scheduling the next one. A basic understanding of this concept is beneficial if you are new to programming or if you want to improve your programming skills. In this article, we discuss what asynchronous programming is, learn how it works, list some benefits and share some examples to help you understand it better.

What Is Asynchronous Programming?

Asynchronous programming is a technique that allows for multiple tasks to execute at once, with each process reporting its success or failure to the main process or thread that invoked it. These operations may not execute in a hierarchical or sequential order, and each operation runs independently of all other operations scheduled. This helps achieve outcomes much faster and improves system performance and responsiveness.

Take the example of ordering food from a restaurant. The server takes multiple orders from you and begins to serve the appetiser as soon as it is ready. In parallel, they can also serve some parts of the main course. They do this instead of waiting for the entire course to be prepared. This ensures that you do not wait for the completion of all the orders before you can start eating. As an example of an asynchronous process, the servers serve a variety of dishes simultaneously.

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Benefits Of Asynchronous Programming

The advantages of using this parallel programming technique include:

  • Using async programming enhances speed, responsiveness and user experience.

  • By eliminating page load delays, subsequent page refreshes are no longer necessary.

  • You can use over one feature at a time, even if other requests are running.

  • An asynchronous application requires few resources and is highly scalable.

  • The response time of one request does not affect the response time of others.

  • When one thread fails, the others continue to render.

  • A built-in callback lets you create custom error messages.

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Async Programming Concepts

Some async programming concepts include:

  • Non-blocking: It refers to a program that does not block the execution of subsequent actions.

  • Multi-threading: Multi-threading refers to a program running multiple threads, where each thread runs a process.

  • Multiprocessing: Multiprocessing refers to a program running various processes concurrently, where each process can run one or more threads.

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Asynchronous Vs. Synchronous Programming

You can think of a movie counter queue as an example of synchronous programming. It is not possible for you to get a ticket until everyone in front of you has received theirs. Assigning tickets, in this case, is sequential. The differences between async programming and synchronous programming, also known as sync programming, include:

  • Parallel processes: In async programming, operations or program can run simultaneously. Due to sync's single-thread design, only one operation or program runs at a time.

  • Multiple requests: Due to its non-blocking nature, async can send multiple requests to the server. With sync programming, an application sends the server one request at a time and waits for the server to respond.

  • Increased throughput: Due to its ability to run multiple operations simultaneously, async increases the throughput. Sync applications are slower and more methodical.

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Example Of Async Programming

You can use async programming by splitting a complex task into various components that run in parallel. These components do not rely on each other for their completion and there is no specific order defined for their execution. After successfully executing the components, you can combine their individual outputs into a single output. This makes your code more efficient, responsive and effective. Here is an example to understand async programming:

Consider that you are performing an arithmetic operation on a set of two numbers, A and B. The arithmetic operations include addition, subtraction, multiplication and division. In a sync program, all these operations occur in sequence. This process takes four steps to complete. With async programming, you can perform the four arithmetic operations in parallel. This makes the execution faster. With concurrent data processing, the program can load the numbers into memory and perform four instructions simultaneously. This ensures that one instruction does not require waiting while the others are being executed.

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When To Use Async Programming?

Here are some instances of using async programming in your daily tasks:

Running longer tasks

For applications that contain multiple sub-tasks that require a longer time to process, programmers can consider implementing async programming. Consider the example:

You have implemented an algorithm that receives multiple document files and extracts various details such as name, gender, age, address, unique ID and phone number. The company has to process one lakh records every day. You can implement async programming where the program receives multiple documents in parallel, extracts the required information and proceeds to the next set. In case there is an error in extraction, the program does not halt and continues to process the other documents in the queue.

Had you implemented sync programming, the program would process only one document at a time with chances of halting in case of erroneous or corrupted documents.

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Minimising idle time

Async programming minimises the idle time between tasks and helps complete a task faster. Consider the example:

When you request information from three different servers, synchronous programming would process each request independently. With async programming, the first server might provide the information quickly, but the second might experience a lag. Here, you might skip the second server and get the required data from the third one instead. By switching tasks, you can minimise idle time and resume collecting information from the second server, after having collected it from one and three.

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Improving operational efficiency

For applications with many tasks, programmers can consider using async programming. It allows one or more tasks to progress independently, rather than sequentially. The user benefits from increased responsiveness and improved overall performance. Consider the example:

You have a travel website that provides various details such as accommodation, restaurants, inter-city travel, user reviews and pricing. Users may look for information from multiple sources at once, which requires sending multiple Hypertext Transfer Protocol (HTTP) requests for each one of them. You can optimise this by using async programming where you send multiple HTTP requests in parallel and provide the user with all the requested details at once. This improves the operational efficiency of your website.

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Making a responsive user-interface

Using async programming enhances the user experience of an application by allowing users to explore various features in parallel while they wait for the primary feature to load. Consider the example:

Consider a mobile application which contains three buttons. You can click on the first button to fetch the live tennis scores. The second button gives you the current weather, wind speed, temperature, precipitation and humidity. The third button allows you to switch the application between themes such as grey, light and dark. When users click on the first button, it is also necessary for the application to allow them to click on the other two buttons. It is essential that the buttons work independently of each other. Async programming can help achieve this functionality.

This ensures that the users do not have to wait while a feature loads and that they can remain engaged by browsing the other features available.

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Making an application scalable

Apps that are scalable can accommodate more users and adapt to the changing needs of the organisation. Scalability pertains specifically to the app's backend, database and servers. Review the example:

Consider a back-end service that performs a lot of database requests, including reading and writing operations. In the event of many requests which require completion within strict time requirements (SLA), it is beneficial to use async programming. With the execution of multiple requests in parallel and optimal resource utilisation, the application becomes scalable.

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Limitations Of Async Programming

The limitations of async programming include:

  • The code written to implement async programming can get complex and difficult to understand.

  • Some tasks in async programming may fail.

  • If a service calls a database that cannot scale, using async can be an overhead.

  • Development might be cumbersome because of a lot of callbacks and recursive functions.

  • In the absence of callbacks, users cannot know if a request has succeeded or failed.

  • An initial delay in rendering a page can have a negative impact on the user experience.

  • Search engines may have difficulty crawling web apps with asynchronous loading.

  • Some programming languages may make asynchronous scripting difficult to implement.

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