SAA-C03 Design Cost-Optimized Architectures Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Enable S3 Cross-Region Replication from the us-west-2 source bucket to a destination bucket in us-east-1, and update the app to read from the us-east-1 bucket.

  Why this is correct

  S3 Cross-Region Replication (CRR) creates an asynchronous, automatic copy of every object in the us-west-2 source bucket to a destination bucket in us-east-1. By updating the application to read from the us-east-1 bucket, all GET requests stay within the same Region, eliminating inter-Region data transfer charges that currently accrue for each cross-Region read. Since CRR transfers each object once during replication (rather than on every read), this pattern becomes cost-effective when the application frequently reads the same large objects. You must still account for a short replication lag, so the app should tolerate eventual consistency for newly written objects.

• ✗

  Create an interface VPC endpoint for S3 in us-east-1 and keep all object reads pointing to the us-west-2 bucket.

  Why it's wrong here

  An interface VPC endpoint for S3 in us-east-1 provides private connectivity to S3 via AWS PrivateLink, but it only works for S3 buckets in the same Region as the endpoint. If the bucket remains in us-west-2, requests from the us-east-1 EC2 instance must still cross the U.S. inter-Region network, incurring standard inter-Region data transfer fees. The endpoint removes the need for a NAT gateway or internet path, but it does not change the physical location of the data or the cost of moving bytes between Regions.

  When this WOULD be correct

  If the S3 bucket were in the same region as the VPC endpoint (e.g., both in us-east-1) and the goal were to avoid public internet exposure or reduce data transfer costs within a region, an interface VPC endpoint would be correct.

• ✗

  Use VPC peering between two regions and route all requests to the us-west-2 bucket over the peering link.

  Why it's wrong here

  VPC peering connects two VPCs over the AWS global network, but it provides connectivity at the VPC/instance level, not for S3 endpoints. S3 is a regional managed service, and you cannot route its traffic through a VPC peering connection—S3 requests must still use either a public endpoint, a gateway endpoint, or an interface endpoint local to the Region. Even if you placed a VPC endpoint in the us-west-2 VPC and peered it, the inter-Region traffic between us-east-1 and us-west-2 would still be measured and billed by AWS as inter-Region data transfer, so peering adds complexity without addressing the cost driver.

  When this WOULD be correct

  If the application needs to access an S3 bucket in another region with lower latency and the data transfer costs are not a concern, or if the bucket is in the same region as the VPC (e.g., both in us-east-1), VPC peering could provide private connectivity without traversing the public internet.

• ✗

  Use Route 53 latency-based routing to send users to a us-west-2 web endpoint and keep the S3 bucket unchanged.

  Why it's wrong here

  Route 53 latency-based routing controls how end users are directed to HTTP endpoints, so moving or adding a web endpoint in us-west-2 would affect only the client-facing tier. It does nothing to change the data path between the EC2 application in us-east-1 and the S3 bucket in us-west-2; the app's reads still traverse the inter-Region network and incur the same per-GB data transfer charges. If the goal is to reduce S3 read costs, you need to either move the application to the same Region as the bucket or copy the data to the application's Region—not redirect users.

  When this WOULD be correct

  This option would be correct if the application needed to minimize latency for global users accessing a web application hosted in multiple regions, and the S3 bucket was in the same region as the web endpoint, with no requirement to replicate data or reduce inter-Region transfer costs.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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