Well, you could definitely front two versions of your application lambda function with a traffic splitter lambda function that would send 99% of traffic to the production alias and 1% to the canary (or whatever the number you wanted was. See how to call one lambda from another: http://stackoverflow.com/questions/31714788/can-an-aws-lambd... and aliases: http://docs.aws.amazon.com/lambda/latest/dg/versioning-alias...

This post might also be of interest: https://blog.jayway.com/2016/09/07/continuous-deployment-aws...

Note, I have never done this, this is just how is approach it.