Scaling Node.js AWS Lambda Functions for High Traffic
5 mins read

By: vishwesh

Scaling Node.js AWS Lambda Functions for High Traffic

AWS Lambda is a serverless computing service provided by Amazon Web Services (AWS). It allows you to run your code without the need for provisioning and managing servers. AWS Lambda is great for building applications that need to scale quickly in response to user traffic. Node.js is a popular programming language for building serverless applications because it's lightweight and efficient. In this article, we'll explore how to scale Node.js AWS Lambda functions for high traffic.

Understanding AWS Lambda

AWS Lambda is a service that runs your code in response to events. An event can be a file upload to Amazon S3, an API request, or a scheduled task. AWS Lambda allows you to write your code in a variety of programming languages, including Node.js.

AWS Lambda functions are stateless. That means they don't store any information about previous invocations. This makes them easy to scale because you can run multiple instances of the same function without worrying about conflicts.

Building a Node.js AWS Lambda Function

Let's start by building a simple Node.js AWS Lambda function. We'll create a function that takes a number as input and returns the square of that number.

exports.handler = async (event) => {
  const number = parseInt(event.number);
  const square = number * number;
  return {
    statusCode: 200,
    body: JSON.stringify({
      square: square

This function takes an event object as input, which contains a property called "number". We parse that number and calculate its square. We then return a JSON object that contains the square value.

Testing the Function

To test the function, we need to create a test event. In the AWS Lambda console, click on "Test" and create a new test event with the following JSON:

  "number": 5

Click "Test" and you should see the result:

  "statusCode": 200,
  "body": "{\"square\":25}"

This means our function is working correctly.

Scaling the Function

Now let's talk about scaling the function. By default, AWS Lambda runs a single instance of your function. If you need to handle more traffic, you can increase the number of instances.

To increase the number of instances, you need to configure the "Concurrency" setting. This setting controls how many instances of your function can run concurrently. By default, it's set to 1. You can increase this number to handle more traffic.

To change the "Concurrency" setting, go to the AWS Lambda console and click on your function. Click on "Concurrency" and change the value to the desired number.

Keep in mind that increasing the number of instances will also increase your costs. AWS charges for the number of requests and the duration of the function.

Using AWS API Gateway

To handle HTTP requests, you can use AWS API Gateway. API Gateway allows you to create RESTful APIs that integrate with AWS Lambda functions.

To use API Gateway, you need to create an API and a resource. You can then create a method that integrates with your AWS Lambda function. Finally, you can deploy your API to a stage, such as "prod" or "dev".

Here's an example of how to create an API Gateway that integrates with our Node.js AWS Lambda function:

  1. Go to the AWS API Gateway console and click on "Create API".
  2. Choose "REST API" and click on "Build".
  3. Create a resource and a method. For example, you can create a resource called "/square" and a method called "GET".
  4. In the method settings, choose "Lambda Function" as the integration type.
  5. Choose your AWS Lambda function and click on "Save". 6. Deploy your API to a stage, such as "prod" or "dev".

Now you can test your API by making a GET request to the URL of your API. For example, if your API URL is, you can make a GET request to This will return the square of the number 5.

API Gateway allows you to handle a large number of HTTP requests and distribute the load across multiple instances of your AWS Lambda function. You can configure API Gateway to handle throttling and caching to improve performance.

Optimizing the Function

To optimize the performance of your Node.js AWS Lambda function, you can use the following techniques:

  1. Reduce the size of your deployment package. AWS Lambda has a limit of 250 MB for the size of your deployment package. You can reduce the size of your package by removing unnecessary dependencies and using only the libraries that you need.
  2. Use environment variables to store configuration settings. This allows you to change the settings without redeploying your function.
  3. Use the AWS SDK for Node.js to interact with other AWS services. The SDK provides a streamlined way to access AWS services and reduces the latency of your function.
  4. Use connection pooling to reuse database connections. This can improve the performance of your function by reducing the overhead of creating new connections.


Node.js AWS Lambda functions are a great way to build scalable and efficient applications. By following the techniques outlined in this article, you can scale your Node.js AWS Lambda function to handle high traffic. Remember to optimize your function by reducing the size of your deployment package, using environment variables, using the AWS SDK for Node.js, and using connection pooling.

AWS Lambda and API Gateway are powerful tools that allow you to build serverless applications with ease. With a little bit of configuration, you can handle a large number of HTTP requests and distribute the load across multiple instances of your function.

Happy scaling!

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