Postcards from Lambda @ the Edge

I first saw Lambda@Edge at re:Invent a couple of years back and wasn’t sure what to make of it. The demo showed how you could manipulate http headers in-flight but the audience was in a post-lunch sugar-crash full of ‘so what?’. It wasn’t the presenter’s fault —some next-level concepts just weren’t landing their punches with the crowd. I mean, who needs to interfere with the CDN, right?

Recently we started a CloudFront-heavy project that performs all sorts of optimization voodoo for webpages. That’s when I remembered back to the Lambda@Edge presentation and a few lightbulbs started to flicker. To test this, we quickly moved some code into functions at The Edge and saw some blistering performance gains. While there was nothing particularly amazing about the code we wrote, getting it working has been a trial like never before. Let’s cover the gotchas before the gold.