There’s nothing special about connecting into AWS Lambda when you do it from Apigee. The same possibilities apply, as if you were connecting into AWS Lambda from anything external to AWS. I am not an expert in AWS Lambda, but I think one way you can invoke Lambda from the internet is via function URLs.
If you don’t want to use the access key ID and secret key, in other words if you don’t want to sign requests, then basically, as I understand it, you will be allowing unauthenticated access into your AWS Lambda function. Anyone will be able to call it. In that case you may wish to implement some sort of custom authorization inside the Lambda function. For that you are on your own.
I am not aware of “temporary” access key IDs and secret keys, in AWS. (I’m not an AWS expert. I work for Google) If these temporary credentials work just like the permanent credentials, then I guess it would work the same.
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