Update Runtimes for Lambda within a cloud formation Stack

Question

Current Setup
1. Cloud Formation stack that uses 2 lambda functions
2. Both lambda functions are currently using python3.7 runtimes

After reading documentation it appears there are a few ways to update this.
1. In the Cloud formation template change the runtimes to the appropriate version
2. In the lambda function page change the runtime settings

I am assuming that the cloud formation has precedence over the runtime settings in the function.

I am mainly looking for the safest way to do this as it is a production system. Seems like I could use a change set to test the change and rollback if needed. 
What would be the proper way to go about this update?
Any help is appreciated.

Answer

Hello.

As you know, if you are creating Lambda with CloudFormation, you can upgrade it by changing the version of the parameter "Runtime".  
If a problem is discovered after upgrading, I think it can be resolved by changing to the original version again using CloudFormation.  
Before upgrading in production, we recommend that you always test the code you currently use in Lambda to ensure that it works correctly in the upgraded version.  
https://docs.aws.amazon.com/ja_jp/AWSCloudFormation/latest/UserGuide/aws-resource-lambda-function.html#cfn-lambda-function-runtime

Update Runtimes for Lambda within a cloud formation Stack

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