When CloudFront receives a request, you can use a Lambda function to generate an HTTP response that CloudFront returns directly to the viewer without forwarding the response to the origin. Generating HTTP responses reduces the load on the origin, and typically also reduces latency for the viewer.

For this setup, do the following: 1.    Create a custom AWS Identity and Access Management (IAM) policy and execution role for your Lambda function. 2.    Create Lambda functions that stop and start your EC2 instances. 3.    Create CloudWatch Events rules that trigger your function on a schedule. For example, you could create a rule to stop your EC2 instances at night, and another to start them again in the morning.

Lambda authorizers–A Lambda authorizer is simply a Lambda function that you can write to perform any custom authorization that you need. There are two types of Lambda authorizers: token and request parameter. When a client calls your API, API Gateway verifies whether a Lambda authorizer is configured for the API method. If it is, API Gateway calls the Lambda function.In this call, API Gateway supplies the authorization token (or the request parameters, based on the type of authorizer), and the Lambda function returns a policy that allows or denies the caller’s request.API Gateway also supports an optional policy cache that you can configure for your Lambda authorizer. This feature increases performance by reducing the number of invocations of your Lambda authorizer for previously authorized tokens. And with this cache, you can configure a custom time to live (TTL).To make it easy to get started with this method, you can choose the API Gateway Lambda authorizer blueprint when creating your authorizer function from the Lambda console.

Develop a Lightweight Project With the Help of AWS, Lambda and Serverless

Lambda@Edge lets you run Lambda functions at AWS Regions and Amazon CloudFront edge locations in response to CloudFront events