Using AWS Lambda with CloudFront Lambda@Edge - AWS Lambda

Using AWS Lambda with CloudFront Lambda@Edge

Lambda@Edge is an extension of AWS Lambda that lets you deploy Python and Node.js functions at Amazon CloudFront edge locations. A common use case of Lambda@Edge is to use functions to customize the content that your CloudFront distribution delivers to your end users. Invoking these functions 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. CloudFront then invokes your Lambda function by sending an event. You can have CloudFront invoke your Lambda function when the following 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)

Conceptual graphic that shows the CloudFront events that can trigger a Lambda function.

Lambda@Edge supports a limited set of runtimes and features. For details, see Requirements and restrictions on Lambda functions in the Amazon CloudFront developer guide.

The following is an example of a CloudFront event.

Example CloudFront message event
{ "Records": [ { "cf": { "config": { "distributionId": "EDFDVBD6EXAMPLE" }, "request": { "clientIp": "2001:0db8:85a3:0:0:8a2e:0370:7334", "method": "GET", "uri": "/picture.jpg", "headers": { "host": [ { "key": "Host", "value": "" } ], "user-agent": [ { "key": "User-Agent", "value": "curl/7.51.0" } ] } } } } ] }

For more information about using Lambda@Edge, see Using CloudFront with Lambda@Edge.