To reduce risk when releasing a new version of an existing Lambda function, you need to split traffic between the current version and the new version for testing. Which approach meets this requirement?

Creating a function alias and configuring it to distribute traffic between two Lambda versions is the correct approach. Lambda aliases allow you to point to a specific Lambda function version and can be configured with a weighted distribution to send a percentage of traffic to one version and the remaining to another. This enables canary deployments and A/B testing directly within Lambda. Using a weighted routing policy in Route 53 is incorrect because Route 53 routes traffic to endpoints (like ALBs or EC2 instances), not directly to different Lambda function versions. An Application Load Balancer (ALB) cannot directly split traffic between different versions of a single Lambda function; it routes to target groups, which would typically contain separate Lambda functions or other compute resources. Packaging the new version as a Lambda layer is incorrect because layers are used for sharing code and dependencies, not for managing traffic distribution between function versions.