3 developers are working with you on a Lambda function that calls AWS SES to send email notifications to clients who have successfully registered with your application. You are now publishing a version of the function. But while doing so, you get a 412 error for PreconditionFailedException. What can you do to debug and resolve the error?

Answer options:

A.Reduce the size of your code and try again.
B.Call the GetPolicy API to get the revisionId and publish a version again.
C.Call the GetAlias API to get the revisionId and publish a version again.
D.Use the UpdateAlias API to publish a version by updating Lambda function Alias.

Answer: C
Option A is incorrect as large size code will not trigger a precondition error. It will trigger a code storage exception error.
Option B is incorrect as the GetPolicy API will return the revissionId of the policy instead of the function needed to correct. 
Option C is CORRECT as per the API documentation. A GetFuncton or GetAlias call will return the right revisionId, and then with that, the new version can be published. Lambda will trigger an error when the revisionId in the request doesn’t align with the current version revisionId. This is often used to protect against a racing condition when multiple people are working on the same function.
 Option D is incorrect. The update API will not actually work as it will throw an exception for the same reasons. 
Reference:
https://docs.aws.amazon.com/lambda/latest/dg/API_PublishVersion.html