Do you really know how AWS Lambda@Edge compares to CloudFront Functions? Here’s a brief summary.
Both services let you run code at the edge with Amazon CloudFront, but they differ significantly in capabilities and use cases:
- Latency & scale positioning: CloudFront Functions runs at edge locations (much closer to the user, there are 200+ worldwide) and are optimized for extremely high scale and low latency. Lambda@Edge runs in regional edge caches (only 13 at the moment) and is slightly higher latency but way more capable in many ways.
- Runtime & language: CloudFront Functions are JavaScript only: ECMAScript 5.1 (dating back to the Mesozoic era), so you’ll be missing on ES6+ awesome features, although you could transpile to ES5 if you really need it. Lambda@Edge supports up to Node.js 22 and Python 3.13 at the moment (unlike regular Lambda, which also supports Ruby, Java, Go, and .NET Core).
- Trigger points: CloudFront Functions supports only the viewer request and viewer response events. Lambda@Edge supports those plus origin request and origin response events.
- Execution limits & environment: CloudFront Functions impose extremely scrict limits in order to remain lightweight: max. size is only 10 KB, max. memory just 2 MB, a mere 1ms of max. execution time, no network or file system access, no request body access. Lambda@Edge has much higher limits (up to 30 seconds duration in origin triggers, tens of GB memory) and supports network access, file system, request body, and external AWS services.
- Cost & complexity: because CloudFront Functions are simpler and constrained, they are generally cheaper and easier to manage for lightweight tasks. Lambda@Edge has more overhead and higher cost potential due to its richer feature set.
What’s each best suited for?
- CloudFront Functions: best for very lightweight, high throughput, ultra low latency tasks such as modifying headers, rewriting URLs, normalizing cache keys, simple redirects or request authorization with minimal logic.
- Lambda@Edge: best when you need network or external service integration, access to request bodies or file system, origin level request or response manipulation, modern JS or Python runtimes, or way more flexible logic than what the edge optimised CloudFront Functions environment allows.