While accessing other AWS services and components from inside your Lambda functions, you can make use of AWS's Simple Token Service (STS) to ensure session-based access, which will essentially add an extra layer of security. As we have already discussed, and learned how to use, STS credentials in our code, we will skip over to the documentation links.
The official documentation of AWS STS will help you understand how session-based access works: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp.html.
And this is the Boto3 Python Documentation for using STS credentials inside Python code: http://boto3.readthedocs.io/en/latest/reference/services/sts.html.