AWS Lambda supports versions and aliases to manage deployments safely. An alias is a named pointer to a specific function version (for example, prod → version 5). Importantly, Lambda aliases can be configured with routing configuration to split incoming invocation traffic between two versions. This enables canary or linear deployments where most traffic goes to the stable version and a small percentage goes to the new version for testing. If issues occur, the developer can quickly shift traffic back by updating the alias.

Option B is the native, simplest, and recommended solution for Lambda traffic shifting.

Option A is not correct because Route 53 weighted routing can split DNS queries between endpoints, but it does not natively target Lambda versions directly for most invocation patterns, and it’s not the standard mechanism for Lambda version traffic shifting.

Option C is unnecessary and adds operational overhead. ALB can invoke Lambda targets, but splitting between Lambda versions is more naturally handled by aliases without provisioning and managing an ALB.

Option D misunderstands layers: layers are for dependencies/shared code, not for deploying new versions or traffic splitting.

Therefore, using a Lambda alias with weighted routing between versions meets the requirement.