Lambda functions should have AWS X-Ray active tracing enabled

How to fix it

In the console

Lambda → Functions → the function → Configuration → Monitoring and operations tools → Additional monitoring tools

Lambda service traces

Enable (tracing mode Active)

Execution role

For the CLI or Terraform, attach AWSXRayDaemonWriteAccess; the console adds the permissions itself

Aliases

Publish a new version and point each alias at it; published versions keep the old tracing mode

With the AWS CLI

aws lambda update-function-configuration --function-name <function-name> --tracing-config Mode=Active --region <region>

With Terraform

resource "aws_lambda_function" "this" {
  function_name = var.function_name
  role          = var.execution_role_arn
  filename      = var.deployment_package

  tracing_config {
    mode = "Active"
  }
}