Too Long; Didn't Read
What Causes Malformed Lambda Proxy Response and How to Fix it? Read this article by Taavi Rehemägi, CEO of Dashbird. What causes the error and how to fix it? The error is not a configuration error, but it could very well be that the routine that checks your return value also checks for other things that can be configured from the outside, like from AWS CloudFormation. After all, Lambda can be used for more than just handling API Gateway requests. It could be used to integrate with many AWS services and the Console UI to make it easier to fix the problem.