Lambda@Edge

• Lambda@Edge is an extension of AWS Lambda, a compute service that lets you execute functions that customize the content that CloudFront delivers.

• You can author Node.js or Python functions in one Region, US-East-1 (N. Virginia), and then execute them in AWS locations globally that are closer to the viewer, without provisioning or managing servers.

• Lambda@Edge scales automatically, from a few requests per day to thousands per second.

• Processing requests at AWS locations closer to the viewer instead of on origin servers significantly reduces latency and improves the user experience.

• When you associate a CloudFront distribution with a Lambda@Edge function, CloudFront intercepts requests and responses at CloudFront edge locations.

• You can execute Lambda functions when the following CloudFront events occur:

  • When CloudFront receives a request from a viewer (viewer request)

  • Before CloudFront forwards a request to the origin (origin request)

  • When CloudFront receives a response from the origin (origin response)

  • Before CloudFront returns the response to the viewer (viewer response)

Use Cases

• A Lambda function can inspect cookies and rewrite URLs so that users see different versions of a site for A/B testing.

• CloudFront can return different objects to viewers based on the device they're using by checking the User-Agent header, which includes information about the devices.

  • For example, CloudFront can return different images based on the screen size of their device.

• For example, on a retail website that sells clothing, if you use cookies to indicate which colour a user chose for a jacket, a Lambda function can change the request so that CloudFront returns the image of a jacket in the selected colour.