If you've ever played around with Amazon CloudFront and thought, "Hmm, how do I customize stuff at the edge?" you've probably bumped into CloudFront Functions and Lambda@Edge. And then, naturally, you've wondered: "Wait… aren't these basically the same thing?"
Short answer: kinda.
Real answer: not really.
Let's break it down like you're deciding between a skateboard (fast, lightweight) and a motorcycle (heavier, way more powerful).
CloudFront Functions — the Speedy Little Edge Worker
Think of CloudFront Functions as the edge-compute version of a sticky note: super lightweight, super fast, very cheap, but only meant for small, quick tasks.
What they're great at
- Super fast viewer-request/response handling Your code runs before CloudFront even touches your request.
- Crazy low latency It literally runs at CloudFront POPs — the closest possible place to your users.
- Cheap Pennies. Even cheaper than Lambda@Edge.
- Simple logic URL rewrites, redirects, header tweaks, basic authentication, A/B testing, that kind of stuff.
What they can't do
- No access to the origin request/response events.
- No network calls.
- No file system.
- No long-running or complex logic.
- No heavy libraries — the runtime is tiny and minimal.
Basically: It's fast because it's limited.
Lambda@Edge — the Heavyweight With Superpowers
Lambda@Edge is the older, more powerful sibling. If CloudFront Functions are a scooter, Lambda@Edge is a touring bike with saddlebags and speakers and a cup holder.
What they're great at
- Supports all four CloudFront trigger points Viewer request, viewer response, and origin request/response.
- Can run longer and heavier code Want to modify HTML? Do image processing? Make API calls? You're good.
- Supports more libraries Way more flexible environment than CloudFront Functions.
- Origin-side personalization For example: choose an origin based on cookies or authorization rules.
What they can't do well
- Not nearly as fast as CloudFront Functions (still fast, but not POP-level fast).
- More expensive.
- Deployments take longer — think minutes, not seconds.
- More operational overhead.
Basically: It can do a lot more, but it costs you more.
⚔️ CloudFront Functions vs Lambda@Edge — The Showdown
| Feature | CloudFront Functions | Lambda@Edge |
|---|---|---|
| Latency | Ultra-low (runs at POPs) | Low (runs at regional edge) |
| Cost | Very cheap | More expensive |
| Runtime limits | Tiny (ms-level) | Bigger (up to seconds) |
| Triggers | Viewer request/response only | All 4 (viewer + origin) |
| Use cases | Simple, fast logic | Heavy, complex logic |
| Supports network calls? | Nope | Yes |
| Deployment time | Seconds | Minutes |
🧭 So which one should YOU use?
Here's the simple rule of thumb:
👉 If the logic is simple, fast, and doesn't need external calls → Use CloudFront Functions.
Examples:
- Redirect
/old→/new - Rewrite URLs
- Add/remove headers
- Basic cookie checks
- Serve country-based variations
- Block bots
👉 If the logic requires more power → Use Lambda@Edge.
Examples:
- Fetching data from another API
- Heavy header computation
- Authentication with external services
- Dynamic HTML rewriting
- Modifying origin responses
- Image transformation or content manipulation
🎯 TL;DR
- CloudFront Functions: blazing fast, super cheap, lightweight. Perfect for easy viewer-side logic.
- Lambda@Edge: powerful, flexible, and capable of handling complex workloads — but slower and pricier.
You really shouldn't choose based on which one is "newer" or "cooler."
Just ask yourself: Do I need more power or more speed?
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