How do I troubleshoot Lambda function provisioned concurrency failure issues?

Short description

After you set up provisioned concurrency for your Lambda function, the following issues might cause your deployment to fail:

• You invoked the Lambda function with the $LATEST version instead of the function version with configured provisioned concurrency.
• You're using all provisioned concurrency, so Lambda uses standard concurrency to invoke your function and you experience cold starts.
• You're using reserved concurrency.
• There are missing or mismatched environment variables or issues with the Lambda function code.
• Lambda can't access or invoke the function code because of a lack of permissions. 

Resolution

To troubleshoot issues with provisioned concurrency, take the following actions:

• Verify that the Lambda function that you use to configure provisioned concurrency isn't set to $LATEST. Unpublished versions of Lambda functions don't support provisioned concurrency.
• In your Lambda function configuration, verify that your provisioned concurrency displays the Ready status.
• Use Amazon CloudWatch Logs to review all logs that your function's code generates to identify potential issues. 
• On the Metrics page of the CloudWatch console, check the ProvisionedConcurrencySpilloverInvocations metric to determine the number of times your Lambda function invoked with standard concurrency.
• Deploy the function without provisioned concurrency. Then, test the Lambda function.
• Check if you configured reserved concurrency for the Lambda function. Reserved concurrency limits a function's ability to scale up.
• Check your Lambda environment variables to make sure that they're correct.
• Check that the services and accounts you use have the permission to invoke the Lambda function. 

If the preceding troubleshooting steps don't resolve your issue, then contact AWS Support. Include the following information in your support case:

• The Lambda function's ARN.
• The workflow on the Lambda function setup with all services.
• Details about whether the issue is intermittent or continuous.
• Complete CloudWatch logs in .txt file format from when the issue occurred.
  Note: The logs help identify Lambda function errors that include timeout issues, init durations, and permissions issues.
• The timestamp of the issue with the time zone or timestamp in UTC.

Note: For security and privacy reasons, AWS Support doesn't have access to customer CloudWatch logs.

For more troubleshooting information, see Lambda: cold starts with new versions.

Note: You incur additional costs when you use provisioned concurrency. To keep provisioned concurrency costs low, it's a best practice to schedule provisioned concurrency usage for your organization.

Related information

Troubleshoot invocation issues in Lambda