AWS Lambda
Developer Guide


Sets a limit on the number of concurrent executions available to this function. It is a subset of your account's total concurrent execution limit per region. Note that Lambda automatically reserves a buffer of 100 concurrent executions for functions without any reserved concurrency limit. This means if your account limit is 1000, you have a total of 900 available to allocate to individual functions. For more information, see Managing Concurrency.

Request Syntax

PUT /2017-10-31/functions/FunctionName/concurrency HTTP/1.1 Content-type: application/json { "ReservedConcurrentExecutions": number }

URI Request Parameters

The request requires the following URI parameters.


The name of the lambda function.

Name formats

  • Function name - MyFunction.

  • Function ARN - arn:aws:lambda:us-west-2:123456789012:function:MyFunction.

  • Partial ARN - 123456789012:function:MyFunction.

The length constraint applies only to the full ARN. If you specify only the function name, it is limited to 64 characters in length.

Length Constraints: Minimum length of 1. Maximum length of 140.

Pattern: (arn:(aws[a-zA-Z-]*)?:lambda:)?([a-z]{2}(-gov)?-[a-z]+-\d{1}:)?(\d{12}:)?(function:)?([a-zA-Z0-9-_]+)(:(\$LATEST|[a-zA-Z0-9-_]+))?

Request Body

The request accepts the following data in JSON format.


The concurrent execution limit reserved for this function.

Type: Integer

Valid Range: Minimum value of 0.

Required: Yes

Response Syntax

HTTP/1.1 200 Content-type: application/json { "ReservedConcurrentExecutions": number }

Response Elements

If the action is successful, the service sends back an HTTP 200 response.

The following data is returned in JSON format by the service.


The number of concurrent executions reserved for this function. For more information, see Managing Concurrency.

Type: Integer

Valid Range: Minimum value of 0.



One of the parameters in the request is invalid. For example, if you provided an IAM role for AWS Lambda to assume in the CreateFunction or the UpdateFunctionConfiguration API, that AWS Lambda is unable to assume you will get this exception.

HTTP Status Code: 400


The resource (for example, a Lambda function or access policy statement) specified in the request does not exist.

HTTP Status Code: 404


The AWS Lambda service encountered an internal error.

HTTP Status Code: 500


Request throughput limit exceeded

HTTP Status Code: 429

See Also

For more information about using this API in one of the language-specific AWS SDKs, see the following: