Understanding Synchronous and Asynchronous Callouts

Oct 13, 2025 by talynt.org 35 views

Introduction

In today's fast-paced and highly competitive business landscape, the need for efficient and scalable systems has never been more pressing. As a developer, one of the key challenges you may face is optimizing your code to handle large volumes of data and requests without compromising performance. In this article, we will explore the process of refactoring an Apex synchronous callout to an asynchronous one, with a focus on enhancing performance and scalability.

Understanding Synchronous and Asynchronous Callouts

Before we dive into the refactoring process, it's essential to understand the difference between synchronous and asynchronous callouts.

Synchronous Callouts

A synchronous callout is a type of callout that blocks the execution of the current thread until the callout is completed. This means that while the callout is in progress, the current thread is unable to perform any other tasks. Synchronous callouts are typically used for short-lived operations, such as retrieving a small amount of data from an external system.

Asynchronous Callouts

An asynchronous callout, on the other hand, is a type of callout that allows the current thread to continue executing other tasks while the callout is in progress. This is achieved through the use of a continuation, which is a callback function that is executed when the callout is completed. Asynchronous callouts are typically used for long-lived operations, such as processing large amounts of data or making multiple requests to an external system.

Benefits of Asynchronous Callouts

So, why should you consider refactoring your Apex synchronous callout to an asynchronous one? Here are some benefits you can expect:

Improved Performance

Asynchronous callouts can significantly improve the performance of your system by allowing multiple tasks to be executed concurrently. This is particularly useful in scenarios where you need to process large amounts of data or make multiple requests to an external system.

Increased Scalability

Asynchronous callouts can also increase the scalability of your system by allowing you to handle a larger volume of requests without compromising performance. This is achieved through the use of a continuation, which allows the current thread to continue executing other tasks while the callout is in progress.

Better Resource Utilization

Asynchronous callouts can also improve resource utilization by allowing the current thread to continue executing other tasks while the callout is in progress. This is particularly useful in scenarios where you need to conserve system resources, such as in a cloud-based environment.

Refactoring an Apex Synchronous Callout to Asynchronous

Now that we've discussed the benefits of asynchronous callouts, let's dive into the process of refactoring an Apex synchronous callout to an asynchronous one.

Step 1: Identify the Synchronous Callout

The first step in refactoring an Apex synchronous callout to an asynchronous one is to identify the callout in question. This may involve reviewing your code to determine which callouts are synchronous and which ones can be refactored to asynchronous.

Step 2: Create a Continuation

Once you've identified the synchronous callout, the next step is to create a continuation. A continuation is a callback function that is executed when the callout is completed. You can create a continuation using the Future class in Apex.

Step 3: Refactor the Callout to Asynchronous

With the continuation in place, the next step is to refactor the callout to asynchronous. This involves modifying the callout to use the Future class and the continuation to execute the callout in the background.

Step 4: Test the Asynchronous Callout

Once you've refactored the callout to asynchronous, the final step is to test the callout to ensure that it's working as expected. This may involve testing the callout in a sandbox environment before deploying it to production.

Example Code

Here's an example of how you might refactor an Apex synchronous callout to an asynchronous one using the Future class and a continuation:

public class MyController {
    public PageReference downloadCsv() {
        // Create a continuation
        Future<PageReference> continuation = new Future<PageReference>() {
            public PageReference get() {
                // Make the callout in the background
                MyCallout callout = new MyCallout();
                return callout.downloadCsv();
            }
        };
    // Return the continuation
    return continuation;
}

}
public class MyCallout {
public PageReference downloadCsv() {
// Make the callout in the background
// ...
return PageReference.getURL('/downloadCsv');
}
}

Conclusion

Introduction

In our previous article, we discussed the benefits of refactoring an Apex synchronous callout to an asynchronous one. We also provided a step-by-step guide on how to refactor an Apex synchronous callout to an asynchronous one. In this article, we'll answer some frequently asked questions (FAQs) about refactoring Apex synchronous callouts to asynchronous ones.

Q: What is the main difference between a synchronous and asynchronous callout?

A: The main difference between a synchronous and asynchronous callout is that a synchronous callout blocks the execution of the current thread until the callout is completed, while an asynchronous callout allows the current thread to continue executing other tasks while the callout is in progress.

Q: Why should I refactor my Apex synchronous callout to an asynchronous one?

A: You should refactor your Apex synchronous callout to an asynchronous one to improve the performance and scalability of your system. Asynchronous callouts can handle a larger volume of requests without compromising performance, making them ideal for long-lived operations.

Q: How do I create a continuation in Apex?

A: You can create a continuation in Apex using the Future class. A continuation is a callback function that is executed when the callout is completed.

Q: What is the `Future` class in Apex?

A: The Future class in Apex is a class that allows you to execute a method in the background. You can use the Future class to create a continuation that is executed when the callout is completed.

Q: How do I refactor a synchronous callout to an asynchronous one?

A: To refactor a synchronous callout to an asynchronous one, you need to create a continuation using the Future class and modify the callout to use the continuation to execute the callout in the background.

Q: What are some best practices for refactoring Apex synchronous callouts to asynchronous ones?

A: Some best practices for refactoring Apex synchronous callouts to asynchronous ones include:

Test thoroughly: Test the asynchronous callout in a sandbox environment before deploying it to production.
Monitor performance: Monitor the performance of the asynchronous callout to ensure that it's not causing any issues.
Use a continuation: Use a continuation to execute the callout in the background and avoid blocking the current thread.
Avoid overusing continuations: Avoid overusing continuations, as they can cause performance issues if not used correctly.

Q: What are some common pitfalls to avoid when refactoring Apex synchronous callouts to asynchronous ones?

A: Some common pitfalls to avoid when refactoring Apex synchronous callouts to asynchronous ones include:

Not testing thoroughly: Not testing the asynchronous callout thoroughly can cause issues in production.
Not monitoring performance: Not monitoring the performance of the asynchronous callout can cause performance issues.
Overusing continuations: Overusing continuations can cause performance issues if not used correctly.
Not using a continuation: Not using a continuation can cause the current thread to block, leading to performance issues.

Conclusion

Refactoring an Apex synchronous callout to an asynchronous one can significantly improve the performance and scalability of your system. By using the Future class and a continuation, you can execute long-lived operations in the background, allowing your system to handle a larger volume of requests without compromising performance. In this article, we've answered some frequently asked questions (FAQs) about refactoring Apex synchronous callouts to asynchronous ones. We hope this article has provided you with the information you need to refactor your Apex synchronous callouts to asynchronous ones.