The main thing about synchronous vs asynchronous programming is choosing whether you want your program to run many tasks at the same time or not. Each has its own use cases and pitfalls, and it’s important to know their differences so you can correctly choose the right type of communication in your projects.
Let’s demystify the whole concept of these architecture models and help you choose the best for your software.
What is Synchronous Programming?
Synchronous refers to operations or events that occur in a specific, sequential order. Each task must be completed before the next one begins, ensuring a linear and predictable flow.
Synchronicity in programming occurs when operations are executed sequentially. An operation is only executed after the previous one is done.
For example, imagine your code is a recipe to cook pasta (no puns with spaghetti code intended). You would:
- Boil water
- Cook pasta (wait until done)
- Prepare sauce (wait until done)
- Serve meal
This means that a potentially complex task may take a while before all its steps are executed and completed. In technical terms, synchronous calls are done in a single thread, and every operation being executed blocks that thread for the execution’s duration.
For the sake of simplicity, let’s imagine we want to sum two numbers and then display the result in a webpage’s HTML element.
In a synchronous project, this is how we could do it:
function performOperation(num1, num2) {
let sum = num1 + num2;
return sum;
}
value = performOperation(1, 2);
document.getElementById("example").innerHTML = value;
Fairly straightforward. We perform the operation, have the value returned to us, and then do what we want with it (in this case, display it).
Pros of Synchronous Processes:
One of the major advantages of sync programming is its simplicity and readability. It is easy to write and understand, especially for beginners. It has a predictable execution with each task completing before the next begins. The Debugging is easier thanks to the linear flow, which simplifies diagnosing bugs or glitches. It’s ideal for short tasks. It demands less computing, with no need to manage event overloads or callbacks.
Cons of Synchronous Processes:
The problem is its blocking behavior. Long-running tasks can block the entire program. It also has limited scalability: Handling multiple tasks concurrently is challenging. Finally, it might lead to inefficient resource utilization. Later tasks may remain idle while waiting for other tasks to complete.
What is Asynchronous Programming?
Asynchronous programming allows tasks to run independently, enabling multiple tasks to be processed at the same time without blocking the main execution thread.
Unlike synchronous operations, asynchronous tasks run independently, allowing other operations to continue without being blocked. Tasks that are not dependent on others can be offloaded and executed at the same time as the main operation, and then report back the result when they are done.
For example, our former example about the code is a recipe for cooking pasta. In asynchronous programming, it would be like if you decided to go multi-tasking mode. It would work like this:
- Boil water
- Prepare sauce (while water boils)
- Cook pasta (wait until done)
- Serve meal
In synchronous programming, your code would follow a streamlined path when a step comes after the other; in asynchronous programming, it would follow two or more paths simultaneously (borrowing more power from the CPU, just as your tasks would require more time management and attention).
For easier tasks, Asynchroncity is not worth it, but for more complex tasks, it’s key. Without asynchronicity, a code would work like a whole restaurant where the owner does all the tasks alone. A single task becomes a bottleneck for all the following tasks.
Asynchronicity in JavaScript can be accomplished through the use of callback functions. Consider our previous example now done asynchronously:
function changeValueDisplay(value){
document.getElementById("example").innerHTML = value;
}
function performOperation(num1, num2, callback) {
let sum = num1 + num2;
callback(sum);
}
performOperation(1, 2, changeValueDisplay);Notice the difference between asynchronous and synchronous in this example?
We’re not explicitly displaying the value after performOperation. This is because performOperation is now responsible for calling a callback (in this case, changeValueDisplay) after the operation is complete to display the calculated value.
You can easily imagine a more complex operation in place of our sum would severely slow down the page loading, were this a synchronous operation. Now, the programmer is no longer concerned with how long the operation takes, but the callback guarantees that after it’s done, however long it takes, the display will be changed.
Important Disclaimer: Asynchronous Programming ≠ Multi-Threading
Asynchronous programming is not the same as multi-threading. Asynchronous programming deals with a single thread of code; multi-threading has many. Multi-threading would be the analog of hiring a cook to make the sauce while you cook the pasta.
Pros of Asynchronous Processes:
It has no blocking execution, which allows multiple tasks to run in parallel, without interfering with each other. It’s ideal for handling long-running tasks. You can send multiple different requests, and, finally, it’s scalable. Asynchronous programming can run many tasks at once.
Cons of Asynchronous Processes:
Asynchronous programming means that the code has increased its complexity. Now the code has callbacks, promises, or async/await patterns, making it harder to read and manage.
Race Conditions might also arise. A race condition is when multiple asynchronous tasks try to access and modify shared data or resources at the same time, leading to unpredictable and potentially incorrect outcomes
It’s also harder to debug: complexity leads to harder-to-hunt bugs. And, finally, it might be unnecessarily complex for simple tasks. If the code is just for executing a simple task, going asynchronous will take more time.
Async vs. Sync Programming: Key Differences
The key difference between async programming and sync programming is that synchronous (sync) code runs one step at a time—waiting for each task to finish before moving on—while asynchronous (async) code starts a task and immediately continues, handling its result later via callbacks, promises, or async/await.
In sync code, you catch errors with simple try/catch blocks around the code that might fail; in async code, you wrap promises or async functions in try/catch (or use .catch() on promises) for clear, non-blocking error flows.
Debugging sync programs is as easy as stepping through each line. However, async debugging often requires tools or detailed logs to follow how tasks fire and resolve over time.
If it sounds confusing, here’s a cheat sheet on synchronous vs asynchronous programming:
| omparison | Synchronous | Asynchronous |
| Execution | Sequential, tasks depend on each other | Independent, tasks run concurrently |
| Blocking | Blocking – each task waits for the previous | Non-blocking – tasks don’t wait |
| Ease of Implementation | Easier to implement and debug | More complex and harder to debug |
| Performance | Not ideal for long tasks | Better for multitasking |
| Ideal Use Case | Short, simple tasks | Long-running tasks (e.g., network operations) |
Is Asynchronous Better Than Synchronous?
The answer depends. When considering async vs sync processing, you have to take into account the type of project you’re developing. Some types of processing are naturally more suited to certain types of projects. Let’s look at some advantages and disadvantages of each and see which is better in what situations.
Async and Sync Use Cases
You’ll want synchronous programming when your project focuses on a single task (especially if it’s computationally heavy) or tasks that are highly dependent and cannot run in parallel:
- Web Pages: By loading a web page synchronously, you make it easier for Search Engine Optimization (SEO) engines to find and categorize your page’s content.
- Video Rendering: This is a task that takes a lot from your CPU (if not most of it), and thus running other tasks in parallel would oversaturate it.
- Simple Calculations: If you are using a Bill Split Calculator, it will take no more than 3-4 calculations in sequence, and they all depend on each other to keep running.
- Command-line scripts: A script that sequentially performs tasks like renaming files, backing them up, and deleting old ones—each step must complete before the next.
You’ll want asynchronous programming when you have a lot of tasks that do not depend on each other, or tasks that take a long time and can be run in the background:
- Database Manipulation: Databases, especially large ones, are notorious for the long times queries.. By using a different thread for that job, you can let the rest of your application function while you wait for the results.
- Dashboards: If you have a complex dashboard with a lot of information to present, you can use different threads to keep each part updated in real-time or as the system can handle.
- Almost Every App On The Planet: The interface and the rest of the app must keep working while you scroll up and down or send messages.
- Microservices back-end: Multiple services (orders, inventory, payments) communicate asynchronously via APIs, handling thousands of requests without stalling.
As a final note, if your project is relatively simple, using asynchronous programming is highly overkill and is generally not advised. Asynchronicity’s speed benefits would be countered by the inherent increase in complexity for your project.
Choosing the Right Approach
If you’re new to programming a project that involves software development, deciding between synchronous and asynchronous programming can be daunting. Consider synch programming if your project requires tasks in a specific order. For example, a web page where each element loads sequentially is better for SEO. It’s more straightforward, making it a good starting point for beginners.
On the other hand, if your project involves tasks that can run independently without affecting each other, like updating different parts of a complex dashboard, async programming might be more suitable. It allows for more flexibility and responsiveness, but is more complex in terms of code management.
Always weigh the complexity of your project against the benefits each method offers. For simple, sequential tasks, stick with synchronous programming. For complex, independent tasks where speed and responsiveness are crucial, consider asynchronous programming. Remember, the key is to match the programming approach to your project’s specific needs.
Conclusion
Asynchronous programming can become a great boon to a complex project, as well as a headache if it’s not handled properly. We hope this article was enlightening when it comes to the differences between synchronous and asynchronous programming, and where best to apply each of them.
If you’re looking for developers for your project, be it synchronous or asynchronous, DistantJob has a large number of expert developers for hire. We have a strict process that helps our clients find the best candidates that fit any company’s needs and culture fit. Don’t hesitate to contact us! We are the best to apply each of them.
FAQ
No, actually, async might be slightly slower than sync. The thing is, your asynchronous program can have a much higher level of throughput than a fully synchronous program. You are not going async to go faster, you are going async to scale the number of tasks. That can lead to more tasks being done per minute, but the code is running a bit slower.
Mixing sync and async can help you a lot to make your code more flexible and efficient. Certain tasks might be synchronous, while others benefit from asynchronous execution to avoid blocking the main thread.
Bring your debugging tools, place breakpoints before and after await statements to observe how code behaves before and after the program yields control. You also might use stepping mechanisms to execute code line by line, which is especially useful in async code to understand the flow of execution. Register both promises and values to the console at various points in your async code, so you can see the flow of execution and detect the problems. If you wish to automate your debugging process, write tests for your async functions and apply proper frameworks.
