AWS CloudFront Explained

What is AWS CloudFront?

AWS CloudFront is a content delivery network, or CDN, that caches and serves content from a global network of edge locations. Instead of forcing every user request to travel all the way to your origin server, CloudFront can serve cached content from a nearby edge location.

This improves performance, reduces latency, lowers load on your backend, and helps build faster internet-facing applications.

Why CloudFront matters in cloud networking

CloudFront is more than just a speed tool. In many AWS architectures, it becomes a core part of the internet-facing network path. It can sit in front of static websites, APIs, media content, and load-balanced applications.

How AWS CloudFront works

CloudFront receives requests from users and checks whether the requested content is already cached at the nearest edge location. If the content is in cache, it responds immediately. If not, it fetches the content from the origin, stores it according to cache rules, and then returns it to the user.

User requests https://app.example.com
        |
        v
Route 53 resolves domain to CloudFront
        |
        v
Request reaches nearest CloudFront edge location
        |
        v
CloudFront checks cache
   |                     |
   | Cache hit           | Cache miss
   v                     v
Serve content         Fetch from origin
directly from edge    (S3 / ALB / EC2 / API)
        |                     |
        v                     v
 Fast response         Response cached at edge
                              |
                              v
                     Content returned to user

Simple traffic flow

1. User requests a website or API endpoint.
2. DNS typically resolves the domain to CloudFront.
3. CloudFront edge location receives the request.
4. If content is cached, CloudFront serves it immediately.
5. If content is not cached, CloudFront requests it from the origin.
6. The response is returned to the user and may be cached for future requests.

Core CloudFront components

1. Distribution

A CloudFront distribution is the main configuration object. It defines how content is delivered, which origin to use, which cache behaviours apply, and which domains or certificates are attached.

2. Edge locations

Edge locations are CloudFront’s global points of presence. Cached content is served from these locations to reduce latency.

3. Origin

The origin is where CloudFront fetches content from when it is not available in cache.

4. Cache behaviour

Cache behaviour controls how requests are handled, which paths are cached, what headers or cookies are forwarded, and how CloudFront communicates with the origin.

CloudFront caching explained

Caching is the main reason many teams adopt CloudFront. When properly configured, it reduces latency and saves backend compute resources.

How caching helps

• Static assets are served faster to users around the world.
• Repeated requests do not always hit the backend.
• Origin infrastructure handles fewer requests.
• Applications often scale better under heavy traffic.

Common caching concepts

Security benefits of CloudFront

CloudFront can improve security posture by reducing direct exposure of origin infrastructure and providing multiple protection features.

• AWS WAF integration: Filter malicious traffic before it reaches the origin.
• AWS Shield integration: Helps protect against DDoS attacks.
• TLS termination: Serve HTTPS content securely to users.
• Signed URLs and signed cookies: Restrict access to protected content.
• Origin Access Control: Protect S3 origins from direct public access.

Real-world CloudFront architecture example

One common pattern for a public web application is shown below:

User
  |
  v
Route 53
  |
  v
CloudFront
  |
  v
AWS WAF
  |
  v
Application Load Balancer
  |
  v
EKS / EC2 application backend
  |
  v
Database / internal services

In this setup:

• Route 53 resolves the domain name.
• CloudFront acts as the global edge delivery layer.
• WAF filters malicious requests.
• The ALB routes valid requests to backend targets.

Static website example

Another common setup is S3 plus CloudFront, where static site content is stored in S3 and CloudFront delivers it globally.

Terraform example for CloudFront

Below is a simple example of a CloudFront distribution in front of an S3 origin.

resource "aws_cloudfront_distribution" "main" {
  enabled = true

  origin {
    domain_name = aws_s3_bucket.site.bucket_regional_domain_name
    origin_id   = "s3-site-origin"
  }

  default_cache_behavior {
    allowed_methods  = ["GET", "HEAD"]
    cached_methods   = ["GET", "HEAD"]
    target_origin_id = "s3-site-origin"

    viewer_protocol_policy = "redirect-to-https"
  }

  viewer_certificate {
    cloudfront_default_certificate = true
  }

  restrictions {
    geo_restriction {
      restriction_type = "none"
    }
  }

  default_root_object = "index.html"
}

What this Terraform does

• Creates a CloudFront distribution.
• Uses an S3 bucket as the origin.
• Redirects HTTP users to HTTPS.
• Defines basic cache behaviour for GET and HEAD requests.
• Sets a default root object for website access.

Common CloudFront mistakes

Caching dynamic content incorrectly

Some teams cache pages or APIs that should not be cached, leading to stale or incorrect responses.

Forwarding too many headers, cookies, or query strings

Over-forwarding can reduce cache efficiency and increase origin requests.

No invalidation strategy

Content updates may not appear quickly if invalidation or versioned filenames are not used properly.

Leaving origin too exposed

If users can bypass CloudFront and hit the origin directly, you lose many of the security and performance benefits.

Wrong origin protocol settings

Misconfigured HTTP/HTTPS settings between CloudFront and the origin can cause connectivity or redirect issues.

CloudFront troubleshooting guide

Practical troubleshooting checklist

• Confirm whether the issue is at DNS, CloudFront, WAF, origin, or application level.
• Check cache settings and recent invalidations.
• Review origin configuration and permissions.
• Inspect forwarded headers, cookies, and query strings.
• Validate TLS and redirect configuration.
• Check whether the origin is healthy and reachable from CloudFront.

CloudFront interview questions

Frequently asked questions

Related cloud networking resources