AWS Global Accelerator and CloudFront are both AWS services that improve application performance and availability, but they operate at different layers of the network stack and serve distinct purposes.
Let’s see Global Accelerator in action. Imagine you have a fleet of EC2 instances in us-east-1 and eu-west-2 serving your application. Your users are spread across the globe. Without Global Accelerator, a user in Australia trying to access your app might be routed through congested internet paths to us-east-1, resulting in high latency.
# Simulate a trace without Global Accelerator
traceroute example.com
Now, let’s introduce Global Accelerator. You create a Global Accelerator accelerator and associate it with two static IP addresses. Then, you configure two endpoint groups, one for us-east-1 and one for eu-west-2, pointing to your EC2 instances. Global Accelerator advertises its static IPs from AWS edge locations worldwide. When a user in Australia attempts to connect, their traffic is directed to the nearest AWS edge location. From there, Global Accelerator uses the AWS global network to route the traffic to the optimal healthy endpoint in your us-east-1 or eu-west-2 region, whichever offers the best performance.
# Simulate a trace with Global Accelerator
traceroute <Global Accelerator Static IP>
The key problem Global Accelerator solves is optimizing the "last mile" of internet routing. Traditional DNS often directs users to the geographically closest server, but the path between the user and that server can be highly variable and congested. Global Accelerator leverages AWS’s private, high-bandwidth network backbone to bypass public internet congestion and provide a more consistent and lower-latency connection. It achieves this by providing static Anycast IP addresses that are advertised from AWS edge locations globally. When a user’s device resolves these Anycast IPs, it’s directed to the nearest AWS edge location. From there, Global Accelerator intelligently routes the traffic over the AWS network to the best-performing healthy endpoint in your configured regions.
CloudFront, on the other hand, is a Content Delivery Network (CDN) focused on caching and delivering static and dynamic web content closer to end-users. It operates at the application layer (Layer 7). When you configure CloudFront, you point it to an origin server (like an S3 bucket or an EC2 instance). CloudFront then caches copies of your content at its edge locations worldwide. When a user requests content, CloudFront serves it from the nearest edge location if it’s cached, significantly reducing latency for frequently accessed assets.
Here’s a CloudFront configuration snippet:
{
"DistributionConfig": {
"CallerReference": "my-unique-id-12345",
"Aliases": {
"Quantity": 1,
"Items": [
"cdn.example.com"
]
},
"DefaultRootObject": "index.html",
"Origins": {
"Quantity": 1,
"Items": [
{
"Id": "my-s3-origin",
"DomainName": "my-bucket.s3.amazonaws.com",
"OriginPath": "",
"CustomHeaders": {
"Quantity": 0
},
"S3OriginConfig": {
"OriginAccessIdentity": "origin-access-identity/cloudfront/E1A2B3C4D5E6F7"
}
}
]
},
"DefaultCacheBehavior": {
"TargetOriginId": "my-s3-origin",
"ForwardedValues": {
"QueryString": false,
"Cookies": {
"Forward": "none"
},
"Headers": {
"Quantity": 0
},
"QueryStringCacheKeys": {
"Quantity": 0
}
},
"ViewerProtocolPolicy": "redirect-to-https",
"MinTTL": 0,
"AllowedMethods": {
"Quantity": 2,
"Items": [
"GET",
"HEAD"
],
"CachedMethods": {
"Quantity": 2,
"Items": [
"GET",
"HEAD"
]
}
},
"Compress": true,
"SmoothStreaming": false
},
"Comment": "My CDN distribution",
"Enabled": true,
"ViewerCertificate": {
"CloudFrontDefaultCertificate": false,
"ACMCertificateArn": "arn:aws:acm:us-east-1:123456789012:certificate/abcdefgh-ijkl-mnop-qrst-uvwxyz123456",
"SSLSupportMethod": "sni-only",
"MinimumProtocolVersion": "TLSv1.2_2021"
},
"HttpVersion": "http2"
}
}
The most surprising thing about Global Accelerator is that it doesn’t care about your application’s health checks as much as it cares about network reachability. It uses TCP-level health checks to determine endpoint availability. If an endpoint is responding to TCP connections, Global Accelerator considers it healthy, even if the application on that endpoint is struggling or returning errors. This means you need to ensure your application layer health checks are robust and that your endpoints are truly serving traffic correctly, because Global Accelerator might keep sending traffic to an endpoint that appears "up" at the TCP level but is functionally degraded.
Global Accelerator is ideal for applications that are not primarily HTTP/S based, or when you need to direct traffic to a fleet of servers across multiple regions for non-web applications like gaming, VoIP, or IoT, where consistent network performance is paramount. CloudFront excels at accelerating the delivery of web content by caching it at the edge. You can even use them together: Global Accelerator can direct traffic to your application servers, and those servers can then serve content that is dynamically generated or fetched from a backend that is itself accelerated by CloudFront.
The next thing you’ll likely encounter is how to manage traffic flow and failover more granularly within Global Accelerator, especially when dealing with multiple regions and different endpoint types.