You can now set a concurrency limit on individual AWS Lambda functions. The concurrency limit you set will reserve a portion of your account level concurrency limit for a given function. This feature allows you to throttle a given function if it reaches a maximum number of concurrent executions allowed, which you can choose to set. This is useful when you want to limit traffic rates to downstream resources called by Lambda (e.g. databases) or if you want to control the consumption of elastic network interfaces (ENI) and IP addresses for functions accessing a private VPC.