Managing AWS Lambda Concurrency Settings with AWS CDK

Understanding AWS Lambda Concurrency

Concurrency in AWS Lambda refers to the number of invocations of a Lambda function that can run simultaneously. By default, AWS Lambda functions have a concurrency limit of 1000, but you can configure this limit to suit your needs. Controlling concurrency is crucial for ensuring the efficient and reliable execution of your serverless applications.

Using AWS CDK to Set Concurrency

The AWS CDK is a development framework for defining cloud infrastructure in code. It allows you to define and provision AWS resources using familiar programming languages. To set the concurrency for a Lambda function using the CDK, you typically use the reservedConcurrentExecutions property when defining the Lambda function. Here’s an example in TypeScript:

const lambdaFunction = new lambda.Function(this, ‘MyLambdaFunction’, {
// other Lambda function configurations
reservedConcurrentExecutions: 10, // Set the concurrency to 10
});

In this example, we’ve set the concurrency limit to 10 for the Lambda function MyLambdaFunction.

Manually Changing Concurrency

Sometimes, you might need to manually modify the concurrency settings of a Lambda function using the AWS Management Console. However, it’s essential to understand that changes made manually in the console do not automatically sync with your CDK code.

Modifying Code vs. Manul Concurrency Settings

It’s important to note that changing the code of your Lambda function and redeploying it using the AWS CDK does not automatically revert any manually changed concurrency settings in the AWS Lambda console. The CDK manages the deployment of your code and the desired state of your infrastructure, but it doesn’t actively monitor or manage the current state of resources.

Reverting Concurrency Settings

If you’ve manually changed the concurrency settings in the AWS Lambda console and want to revert them to the values specified in your CDK code, you need to do the following:

  1. Modify your value in CDK code to set the reservedConcurrentExecutions property back to the desired value (e.g., 11 or 9 in our example).
  2. Redeploy your CDK stack.

After following these steps, the Lambda function’s concurrency settings will be updated to the value specified in your CDK code.

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