,

What is a CDN? And Why Companies Use Fastly to Make Websites Faster

A beginner-friendly guide to Content Delivery Networks (CDNs) and Fastly’s edge platform.

A few weeks ago, I was working on a website migration project where we needed to redirect traffic from old application URLs to new ones. During the discussions, one question kept coming up:

“Can we handle this through Fastly instead of changing the application itself?”

That simple question led me down a rabbit hole of learning more about CDNs, edge computing, caching, and how platforms like Fastly sit between users and web applications.

If you’ve ever wondered:

  • What exactly is a CDN?
  • Why do websites use CDNs?
  • What does Fastly actually do?
  • Why not just serve everything directly from the web server?

Then this article is for you.

Imagine Your Website Lives in One City

Let’s say your website is hosted on a server in New York.

When someone from New York visits your website, the request travels a relatively short distance.

But what happens when a user from Mumbai, Tokyo, Sydney, or London accesses the same site?

Every request still has to travel all the way to New York and back.

While this happens in milliseconds, those milliseconds add up:

  • Slower page loads
  • Higher latency
  • Poor user experience
  • Increased load on your servers

As your audience grows globally, this problem becomes more noticeable.

This is where a CDN comes in.

What is a CDN?

A Content Delivery Network (CDN) is a distributed network of servers located around the world.

Instead of every user connecting directly to your application’s origin server, users connect to the nearest CDN location.

Think of it like this:

If your origin server is a central warehouse, a CDN creates smaller distribution centers across multiple cities.

Instead of shipping every package from the warehouse, you ship from the nearest distribution center.

The result?

Faster delivery and less strain on the warehouse.

How a CDN Works

When a user requests a webpage:

Without a CDN

User → Origin Server → Response

Every request goes directly to the application server.

With a CDN

User → CDN Edge Server → Response

If the content is already cached on the CDN, the user receives it immediately.

If the CDN doesn’t have the content:

User → CDN → Origin Server
                 ↓
             Content
                 ↓
User ← CDN ← Origin Server

The CDN fetches the content, stores it temporarily, and serves it to future visitors.

This process is called caching.

Why CDNs Matter

1. Faster Websites

The biggest benefit is speed.

Users connect to a server closer to them geographically, reducing network travel time.

Even a small reduction in latency can significantly improve:

  • User experience
  • Conversion rates
  • SEO rankings

Google itself considers page speed an important ranking factor.

2. Reduced Server Load

Without a CDN:

10,000 users = 10,000 requests to your server

With a CDN:

10,000 users = Most requests served by the CDN

Your origin server receives far fewer requests.

This means:

  • Lower infrastructure costs
  • Better scalability
  • Improved reliability

3. Better Availability

Imagine your website suddenly goes viral.

Instead of all traffic hitting a single server, CDN edge locations absorb much of the load.

This helps prevent outages and keeps your website responsive.

4. Improved Security

Most modern CDNs provide features such as:

  • DDoS protection
  • Web Application Firewalls (WAF)
  • TLS/SSL management
  • Bot detection

In many cases, the CDN becomes the first line of defense between the internet and your application.

Enter Fastly

Among the many CDN providers available today, one name that frequently appears in enterprise environments is Fastly.

Fastly is more than just a traditional CDN.

It’s often described as an edge cloud platform, because it allows organizations to run logic closer to users rather than solely relying on centralized servers.

What Makes Fastly Different?

Traditional CDNs are primarily focused on caching.

Fastly focuses on caching and edge computing.

This means requests can be modified, redirected, filtered, or secured before they ever reach the origin server.

For example:

User
 ↓
Fastly Edge
 ↓
Application Server

The edge layer can make decisions in real time.

A Real-World Redirect Example

Let’s say an organization decides to retire an old application.

Old URL:

/legacy-app

New URL:

/new-app

One option is to update the application’s server configuration.

Another option is to configure the redirect in Fastly.

The request flow becomes:

User
 ↓
Fastly
 ↓
301 Redirect
 ↓
New Application

The redirect happens at the edge before the request reaches the application server.

Benefits include:

  • Reduced origin traffic
  • Faster redirects
  • Easier centralized management

This is one of the most common enterprise use cases for Fastly.

One Feature I Found Particularly Interesting: Instant Purging

One challenge with caching is stale content.

Imagine updating a webpage, but users continue seeing the old version because it’s cached.

Many CDN providers take time to clear cached content.

Fastly is known for its instant purge capability.

When content changes:

Old Content
     ↓
Cache Purge
     ↓
New Content

The updated version becomes available almost immediately.

For organizations publishing frequently updated content, this can be extremely valuable.

Fastly and APIs

CDNs are often associated with static assets such as:

  • Images
  • CSS
  • JavaScript

But modern applications rely heavily on APIs.

Fastly can also help accelerate API traffic by:

  • Reducing latency
  • Optimizing routing
  • Applying security controls at the edge

This is especially useful for applications serving users across multiple regions.

CDN vs Fastly: What’s the Difference?

A CDN is a category of technology.

Fastly is a specific platform within that category.

It’s similar to saying:

  • Database → PostgreSQL
  • Cloud Provider → AWS
  • CDN → Fastly

Fastly provides standard CDN functionality while adding powerful edge-computing capabilities.

Final Thoughts

As developers, we often focus on application code, databases, and infrastructure. But sometimes the biggest performance improvements come from the layers in between.

A CDN can dramatically improve:

  • Website speed
  • Scalability
  • Reliability
  • Security

And platforms like Fastly show how the edge has evolved from simple caching to intelligent request processing.

The next time you open a website and it loads almost instantly from the other side of the world, there’s a good chance a CDN is helping make that experience possible.

And if you’re working with enterprise websites, APIs, migrations, or redirects, chances are you’ll encounter Fastly sooner rather than later.

In this article:
Share on social media:

Relevant Blogs