Lambda@Edge are executed by associating functions against specific cache behaviors in CloudFront. You can also specify at which point during the CloudFront request or response processing the function should execute (i.e., when a viewer request lands, when a request is forwarded to or received back from the origin, or right before responding back to the end viewer). You to write code using Node.js or Python from the Lambda console, API, or using frameworks like the Serverless Application Model (SAM). When you have tested your function, you associate it with the selected CloudFront cache behavior and event trigger. Once saved, the next time a request is made to your CloudFront distribution, the function is propagated to the CloudFront edge, and will scale and execute as needed. Learn more in our documentation.