Cloudfront-Functions

Right, so you’ve got your CloudFront distribution set up. It’s serving your site, caching your assets, and generally feeling pretty snappy. Now, let’s talk about how to not get pwned. Because a fast website that’s also a gaping security hole is just a liability on amphetamines. We’re going to lock this down properly, and I’ll explain the why behind each step so you’re not just cargo-culting configs. HTTPS: No Exceptions, No Negotiation This isn’t 2012. HTTPS is not an optional nice-to-have; it’s the absolute bare minimum. The internet is a sketchy alleyway, and HTTP is shouting your credit card details down it. CloudFront makes this stupidly easy to enforce.

Alright, let’s talk about CloudFront Functions. You’ve heard of Lambda@Edge, right? Its powerful, do-anything older sibling that can run for up to a second and change almost everything about a request? This isn’t that. CloudFront Functions are the scrappy, hyper-caffeinated cousin. They’re for the small, screamingly fast jobs that need to happen on every single request without adding a millisecond of latency. We’re talking sub-millisecond execution. They are the Usain Bolt of the edge compute world: blindingly fast, but they can’t carry a lot of luggage.

Right, so you’ve decided you want your code to run closer to your users than your origin server. Smart move. Welcome to Lambda@Edge, the feature that lets you shove little bits of Lambda logic into the vast, globe-spanning nervous system of CloudFront. The promise is intoxicating: run your code in dozens of locations worldwide, single-digit millisecond latency, no provisioning servers. The reality is… almost that, but with some very important, often hilarious, caveats. Buckle up.

Right, let’s talk about locking down your S3 bucket when CloudFront is your front door. This is one of those things AWS makes sound complicated, but the core idea is beautifully simple: your S3 bucket should be a hermit that only accepts calls from its one trusted friend, CloudFront. Everyone else—including users with their own AWS credentials—gets the door slammed in their face. We used to do this with an Origin Access Identity (OAI), which was basically a special IAM user. Now, we use the newer, shinier, and frankly more secure Origin Access Control (OAC). OAC uses IAM roles, which is the modern, preferred way for services to talk to each other in AWS. Consider this an upgrade.

Right, so you’ve built something brilliant, and now you want to put it behind a velvet rope. Maybe it’s a premium video course, a paid report, or a members-only cat meme repository. The point is, you need to serve content from CloudFront but only to people who have paid the bouncer. This is where Signed URLs and Signed Cookies come in. They’re two sides of the same coin, both using cryptographic signatures to grant temporary access. The choice between them isn’t about security—they’re equally secure—it’s about the user experience you’re trying to create.

Right, let’s talk about getting your fresh content to the world, or more accurately, getting the old, cached content out of the world. This is cache invalidation, one of the two hard problems in computer science (the others being naming things and off-by-one errors). CloudFront is a brilliant, global-scale caching machine, and like any good cache, it holds onto things. Your job is to tell it when to let go.

Right, let’s talk about the part of CloudFront where you actually get to think: Cache Behaviors. This is where you move from just slapping a CDN in front of your stuff to actually architecting how it behaves. It’s the difference between a bouncer who just checks IDs and one who knows the regulars, the VIPs, and the troublemakers who need a different door. The core idea is simple but powerful: you can tell CloudFront to handle different types of requests differently based on the path pattern. A request for /api/graphql should probably behave very differently than one for /images/cat_picture_1024.jpg. Behaviors let you do that. You create a list of these behaviors, ordered from most specific to least specific (that default * catch-all we talked about last time), and CloudFront walks down that list until it finds a match.

Right, so you’ve told CloudFront where to send your users (the distribution), and how to handle their requests (behaviors). Now we get to the heart of the matter: the Origin. This is the actual, honest-to-goodness source of your content. It’s the server CloudFront goes to, hat in hand, when its own cache is empty. Think of it as CloudFront’s supplier. And just like in the real world, your choice of supplier dictates everything about quality, price, and how much of a headache you’re in for.

Right, let’s talk about CloudFront distributions. This is where you stop thinking of CloudFront as a magic box and start treating it like the complex, configurable beast it is. The first thing you’ll hit when you create one in the console is a choice that seems bafflingly ancient: Web or RTMP. Let’s be direct: you almost certainly want “Web Distribution.” It’s for the modern web—HTTP(S) traffic, your website, your APIs, your static assets. RTMP is a relic, a streaming protocol from the Adobe Flash era. AWS still offers it because, well, someone somewhere is still running a Flash-based video service and paying them a fortune for the privilege. It’s the technical equivalent of a museum exhibit. Let’s move on.