Lambda-Proxy creates an HTTP proxy listening on localhost port 8082. When it receives an HTTP POST request with a very specific structure , it will parse the request, extract the relevant data required for the test, and will invoke your AWS Lambda function using the AWS SDK client.invoke() method. It was created for testing AWS Lambda functions with SQLMap as described here: https://www.puresec.io/blog/automated-sql-injection-testing-of-serverless-functions-on-a-shoestring-budget-and-some-good-music
Why do you think that https://github.com/openwall/john is a good alternative to lambda-proxy