On AWS Lambda Functions you can now set a Concurrency Limits

A Concurrency Limit can be set on individual Amazon Web Service Lambda Functions. The Concurrency Limit that is set to reserve a portion of the account level concurrency limit for a given function. This feature will enable you to control a given function if it reaches a maximum number of concurrent executions permitted which can be set. This is very essential when you want to limit the traffic rates to downstream resources called by AWS Lambda or if you want to manage the consumption of elastic network interfaces and the IP address needed for function accessing a private Virtual Private Cloud.