Synchronous and Asynchronous Programming - Core Differences

07 minutes read
Last updated
June 4, 2022
Diifference between synchronous and asynchronous programming
Programmers often have to work with synchronous and asynchronous programming. But what are the differences between these two and how do they impact the overall performance of your code? In this blog you'll know the core differences and why you should be using one over the other.

Asynchronous programming is a way of writing code that allows multiple tasks to run concurrently. This can be a big advantage when it comes to speeding up your application or making it more reliable.

However, asynchronous programming can also be challenging, as you need to understand the different ways in which your code will execute. In this article, we'll look at the differences between synchronous and asynchronous programming in different languages, and explain how each approach can benefit your project.

What is Synchronous Programming?

A program that executes in a specific order, as dictated by its instructions. This type of programming is often used when the program needs to wait for a particular event before continuing. For example, a program that needs to wait for the user to finish typing their name into a text field.

When to Implement Synchronous Code For Your App?

When to use synchronous vs asynchronous code in different programming languages can be a matter of preference, but it's important to keep in mind the pros and cons of each. In this blog post, we'll discuss when to use each type of code in different languages.

Async/synchronous code:
Synchronous code is often more efficient because it avoids the overhead of calls to the operating system kernel. However, this efficiency comes at a cost- you may need to provide additional synchronization mechanisms (e.g. locks) to ensure that multiple threads don't access the same pieces of data at the same time.

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asynchronous programming can be more convenient for tasks that don't need to be executed as quickly as possible, like reading from a network connection or processing large amounts of data.

However, if your task requires high performance, you may want to consider using an asynchronous library instead.

Languages with synchronous code -

C++: Most C++ algorithms are synchronous by default and must be implemented as such if they need to be used with multiple threads.

Java: Java is one of the few languages that supports both synchronous and asynchronous programming simultaneously. This makes it a good choice if you need to use both types of code together, but it can be more difficult to reason about code that uses asynchronous calls.

Python: Python has a synchronous module that allows you to write code that is synchronized with the global interpreter lock (GIL). This makes Python a good choice for tasks that require high performance, but it can be harder to read and maintain.

Ruby: Ruby also has a synchronous module that allows you to write code that is synchronized with the GIL. This makes Ruby a good choice for tasks that require high performance, but it can be harder to read and maintain.

JavaScript: JavaScript does not have a synchronous module, so all code must be asynchronous. This can make code more difficult to read and maintain, but it also means that JavaScript is well suited for tasks that don't need high performance.

When implementing synchronous code in different languages, it is important to consider the pros and cons of each type of code. 

Advantages of Synchronous Programming

There are many advantages to using synchronous programming techniques. First and foremost, synchronous programming is much more efficient than asynchronous programming. Asynchronous programming can lead to wasted time as tasks wait for each other, while synchronous programming can result in more rapid execution of tasks.

Additionally, synchronous programming is more reliable than asynchronous programming, since errors will be detected and handled before they cause significant damage.

Finally, synchronous programming is easier to learn and use than asynchronous programming, since there are fewer potential headaches associated with incorrect code execution.

Disadvantages of Synchronous Programming

Some disadvantages of synchronous programming are:

  • It can be difficult to achieve concurrency and communication between threads
  • It can be difficult to scale up a synchronous program.
  • Threads may be blocked indefinitely if there is a communication issue

Pros and Cons of  Asynchronous Programming


  • Asynchronous programming can improve the responsiveness of an application.
  • It can help reduce the number of round trips made to the database.
  • It can improve the performance of an application when dealing with large data sets.
  • Since asynchronous programming does not require a response from the code immediately, it is suitable for use in networked applications.


  • Asynchronous programming can be difficult to debug.
  • It can be more complex to write code using asynchronous programming than code using traditional synchronous programming techniques.

What is Asynchronous Programming?

Asynchronous programming is a style of programming in which the execution of a task is not guaranteed to occur in a specific order. This contrasts with synchronous programming, where all code execution is guaranteed to happen in a specific order.

Why use asynchronous programming? There are many reasons why you might choose to use asynchronous programming techniques. Some advantages include the ability to handle tasks asynchronously without blocking the main thread, allowing for more responsive user interfaces.

Additionally, asynchronous programming can be used when you need to do multiple tasks that don't need to happen in the same order. What are some common async languages?

Async languages tend to have lower overhead than synchronous languages and are generally faster due to this. However, there are many different async languages available, so let's find out what is the best one for you?

When to Implement Asynchronous Code For Your App?

One of the most important decisions you'll have to make when writing software is deciding how to handle asynchronous programming - will your code be synchronous or asynchronous? This decision can have a big impact on the speed, reliability, and scalability of your application.

Let's take a look at some common use-cases for asynchronous programming and see when it might be the best solution for your app.

1. When responding to user input is slow or unreliable

In many cases, user input (e.g. submitting a form) can be slow or unreliable, so you may want to handle this by using an asynchronous method instead. This way, the app can continue running while the input is being processed, rather than stopping completely while users wait for a response.

2. When the app needs to keep running in the background

If you need to keep running your app in the background (e.g. for tracking data), then you'll need to use an asynchronous method because otherwise, the app will stop responding immediately when it's put into the background.

3. When scaling up your app?

As your app gets bigger and more features are added, it becomes more difficult to keep everything running smoothly without using an asynchronous method. This is because the app will start to get bogged down by the number of requests it's making and it may not be able to keep up with the demand.

4. When performance is critical?

If you want your app to be as fast as possible, then you'll need to use an asynchronous method. This is because synchronous methods tend to slow down the app overall, no matter how big or small the code snippet is.

5. When an error occurs?

If something goes wrong while your code is running, then you'll need to handle it asynchronously in order to keep the app running. This way, users don't have to wait for the error to be fixed and the app can continue running smoothly.

Synchronous vs. Asynchronous Programming: Which Is Better?

Synchronous programming is the more common type of programming, where tasks are completed in a predefined order. Asynchronous programming, on the other hand, allows tasks to be completed in any order. The main benefit of asynchronous programming is that it can be faster because it does not have to wait for tasks to complete.

However, asynchronous programming can also be more challenging because it requires more code and understanding.

synchronous and asynchronous programming

Some languages, such as Java and Python, support both forms of programming. Other languages, such as C++ and JavaScript, are designed for synchronous programming only. It is important to choose the right language for the task at hand because not all tasks can be performed in an asynchronous manner.

Ultimately, it comes down to which style is better suited for the particular task at hand. If you know exactly what you need to do and there are no dependencies on other processes, then synchronous programming is probably the best option.

However, if you need to work with other programs or make use of multiple threads or CPUs, then asynchronous programming may be a better choice.

If you're asking which is better - synchronous or asynchronous programming - the answer is that it depends on your needs. Synchronous programming is typically more efficient but can be less responsive to user input.

Asynchronous programming, on the other hand, can be more responsive but may not be as efficient.

The biggest advantage of synchronous programming is that it's usually faster. This is because the code runs one after the other in a linear fashion, without any delays. This makes it ideal for tasks like calculations and database operations.

Asynchronous programming, on the other hand, can be faster when there are few delays but it's not always ideal for tasks where speed is critical.

Another thing to consider is how your users will interact with your code. If they're expecting everything to run in a timely manner, then synchronous programming might be best for them.

However, if you want your users to be able to interact with your code while it's running, then asynchronous programming might be better suited.

Ultimately, the choice comes down to what you need and how you plan on using your code.


While both synchronous and asynchronous programming can be useful in different circumstances, there are some key differences between the two that should be considered when choosing which type of programming to use. When using synchronous programming, code is executed as it is written, meaning that all functions must wait for each other to finish before continuing.

Asynchronous programming allows code to run in parallel, which can lead to improved performance but also introduces the risk of errors because not all functions will have been completed by the time the program resumes execution.

Ultimately, if speed is a priority then asynchronous programming might be your best option; however, if you are more concerned with accuracy then synchronous programming might be a better fit.

Hopefully, this article has given you an overview of these two types of programming and helped you make an informed decision about which one would work best for your specific project or situation.

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Manzurul Haque

Manzurul Haque

has contributed in 44 posts
I am a tech enthusiast and explorer, Fulltime Lead Developer and AI, ML specialist. I love to read and write blogs specially about upcoming technological changes and challenges. In my free time, I travel, watch movies, read and spend time with my kid.
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