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AWS SAA-C03SAA-C03 Walkthrough: Cost-Optimised Static Site with S3 and CloudFront
A step-by-step walkthrough of a high-frequency SAA-C03 cost-optimisation question type — designing a cost-efficient global static site delivery architecture. The cost domain is 20% of the exam and trips up many candidates.
The question
A company hosts a static marketing website in an S3 bucket in us-east-1. Users across Europe and Asia report slow load times. The solutions architect must improve global performance at the lowest possible cost. Which solution meets these requirements? A. Create an additional S3 bucket in eu-west-1 and ap-southeast-1. Use S3 Cross-Region Replication to sync content. Update DNS to use latency-based routing. B. Place the S3 bucket behind an Application Load Balancer with a WAF rule that caches responses at the edge. C. Enable Amazon CloudFront with the S3 bucket as the origin. Configure the distribution to cache at edge locations globally. D. Use AWS Global Accelerator to route traffic to the S3 bucket in us-east-1 from the nearest AWS edge location.
[1 mark]
Correct answer: C
Why C is right
CloudFront is the canonical solution for global static asset delivery from S3. It caches content at over 400 edge locations worldwide, meaning users in Frankfurt and Singapore serve cached HTML, CSS, and images from a nearby edge node rather than making a round trip to us-east-1. The S3 origin only receives requests on a cache miss. This reduces latency dramatically and — because CloudFront data transfer costs are lower than S3 transfer costs and the architecture eliminates repeated cross-region S3 egress — is also cheaper than the alternatives.
Why A is wrong
Multi-region S3 with Cross-Region Replication and latency-based routing would improve performance, but it is significantly more expensive. You pay for S3 storage in three regions, replication transfer costs between regions, and the operational overhead of managing multiple buckets and DNS routing policies. It also does not cache at edge locations — users in Amsterdam still connect to eu-west-1, not to an edge node. This fails the "lowest possible cost" constraint.
Why B is wrong
ALB is designed for dynamic workloads with EC2 or container targets. An ALB does not have built-in global edge caching and cannot serve as a CDN. WAF alone does not cache responses. This answer combines two services inappropriately and adds cost without solving the global delivery problem.
Why D is wrong — the common trap
Global Accelerator is a popular distractor on SAA-C03 cost questions. It routes users to the nearest AWS edge location — but it is designed for TCP/UDP applications requiring static IP addresses and failover routing, not for caching static content. Global Accelerator forwards traffic to your origin on every request; it does not cache. It is also priced per accelerator per hour plus data transfer, making it more expensive than CloudFront for static site delivery. When the question says "static site" and "lowest cost", CloudFront is almost always correct over Global Accelerator.
The pattern to remember
Static content + global users = CloudFront
Any time a question describes static assets (HTML, CSS, images, video) needing global delivery, CloudFront is the starting answer. Only deviate if the question introduces a specific constraint CloudFront cannot satisfy.
Global Accelerator ≠ CDN
Global Accelerator improves routing for dynamic TCP/UDP workloads (gaming, IoT, APIs requiring static IPs). It does not cache. Never use it as a substitute for CloudFront on a caching question.
Multi-region replication adds cost, not edge caching
Replicating S3 buckets improves data durability and regulatory compliance — not global performance. CloudFront over a single S3 bucket outperforms multi-region replication for read-heavy static workloads at a fraction of the cost.
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