Understanding async vs sync Handler Functions in AWS Lambda for Node.js

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The Benefits of Using an async Handler Function in AWS Lambda

The Question at Hand

As developers configure AWS Serverless Application Model (SAM) applications, one common personnel confusion revolves around setting up an AWS Lambda function. The default template in many cases promotes the use of an async handler function structured like this:

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The question then arises: Is there any benefit to using an async handler function versus a sync handler function?

Understanding Async and Sync Functions

To grasp the advantages, let's break down what async functions are and how they work.

What Does async Mean?

The async keyword signifies that a function can handle asynchronous operations. Specifically, it comes with two key features:

Return a Promise: An async function automatically wraps its return values in a Promise.

Use of await: Inside an async function, you can utilize the await keyword, which allows the function to pause execution until a Promise is settled.

How AWS Lambda Handles Promises

AWS Lambda is designed to process both synchronous and asynchronous functions efficiently. When you specify an async handler:

Lambda automatically understands that the function will return a Promise.

You can seamlessly integrate operations that require waiting for responses, such as database queries or API calls.

Benefits of Using an async Handler Function

Here are some crucial advantages of adopting async functions in your AWS Lambda applications:

Improved Code Readability

Using async and await leads to cleaner code compared to chaining multiple Promises. It allows developers to write asynchronous code that looks and behaves more like synchronous code, making it easier to understand.

Error Handling Simplified

With async functions, you can utilize try/catch blocks to handle errors more straightforwardly than with traditional Promise chaining. This means less cognitive load when it comes to debugging and managing errors.

Flexibility in Code Execution

By adopting async functions, you have the flexibility to await multiple asynchronous operations, enhancing the way your functions communicate with external systems (such as databases or APIs).

Conclusion

In summary, if you expect your function to handle asynchronous operations and utilize Promises effectively, going with an async handler function is a wise move.

By making this choice, you leverage the full capabilities of modern JavaScript while taking advantage of AWS Lambda's ability to handle asynchronous behavior natively.