Policy to grant public access to an AWS Lambda function.

lambda_policy.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": "*",
            "Action": [
                "execute-api:GET",
                "execute-api:POST",
                "execute-api:Invoke"
            ],
            "Resource": "arn:aws:execute-api:*"
        }
    ]
}