SAA-C03
Deep Dive
For global applications, AWS offers services that reduce latency by routing traffic over its private backbone network. CloudFront, Global Accelerator and Route 53 are the most heavily tested services in the exam — especially in comparisons of when to use each one.
Contents
CloudFront is a CDN (Content Delivery Network)with over 400 Edge Locations and Regional Edge Caches worldwide. It caches content close to users, reducing latency and transfer cost from the origin.
Supported origins
Key features
OAC — Origin Access Control
Lets S3 accept requests only from your CloudFront distribution (private bucket). Replaces the older OAI. The bucket doesn't need to be public. CloudFront signs requests to S3 with SigV4.
Lambda@Edge vs CloudFront Functions
CF Functions
Lightweight JavaScript. Viewer request/response. Sub-ms latency. Millions of req/s.
Lambda@Edge
Node.js / Python. Origin request/response. More powerful, higher latency.
Global Accelerator uses AWS's private backbone network to route traffic globally. It provides 2 static global Anycast IPs. It is not a CDN — it does not cache content.
Key features
Supported targets
ALB
NLB
EC2 instances
Elastic IPs
Unlike CloudFront, the targets are AWS resources (not S3 buckets or custom HTTP endpoints).
| Aspect | CloudFront | Global Accelerator |
|---|---|---|
| Protocol | HTTP/S only | TCP, UDP (any protocol) |
| Caching | Yes — caches at Edge Locations | No — transparent proxy |
| IPs | Variable Anycast IPs (not static) | 2 static Anycast IPs |
| OSI layer | L7 (Application) | L4 (Transport) |
| WAF | Yes — native integration | No (Shield only) |
| Origins | S3, ALB, custom HTTP, API GW | ALB, NLB, EC2, EIP |
Choose CloudFront when:
Choose Global Accelerator when:
Simple
Responds with a single resource (or multiple IPs round-robin). No health checks.
When: A single resource, no failover. Default.
Weighted
Distributes traffic based on weights (e.g.: 80% to us-east-1, 20% to eu-west-1).
When: A/B testing, gradual migration, canary deployments.
Latency-based
Routes to the resource with the lowest latency from the user's location.
When: Multi-region applications where latency matters.
Failover
Primary receives traffic. If the primary fails its health check, traffic routes to Secondary.
When: Active/passive DR. Always paired with health checks.
Geolocation
Routes based on the user's geographic location (country/continent).
When: Regional legal restrictions, localized content.
Geoproximity
Routes based on geographic proximity, with a configurable bias.
When: Fine-tuning regional boundaries with more control than geolocation.
Multi-value
Returns up to 8 records with health checks. The client picks one.
When: Simple distribution with health checks. Not a real load balancer.
A detailed comparison and guide for choosing the right service.
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Test what you just learned
A company has a live video streaming application (RTMP/UDP protocol) with users around the world. They need to reduce latency and have 2 static IPs so users can configure their firewall. Which service is most appropriate?
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