Cost-Effective Private S3 Access via VPC Endpoint

SAA-C03 By islever Editorial Last updated

Design secure access to AWS resources.

Short answer

D Deploy an S3 gateway endpoint to access the S3 buckets.

Question

A company runs an application on Amazon EC2 instances in a private subnet. The application needs to store and retrieve data in Amazon S3 buckets. According to regulatory requirements, the data must not travel across the public internet. What should a solutions architect do to meet these requirements MOST cost-effectively?
  1. Deploy a NAT gateway to access the S3 buckets.
  2. Deploy AWS Storage Gateway to access the S3 buckets.
  3. Deploy an S3 interface endpoint to access the S3 buckets.
  4. Deploy an S3 gateway endpoint to access the S3 buckets. Correct Answer

Key Takeaways

The question tests the distinction between Interface and Gateway endpoints, with the common trap being the selection of Interface endpoints due to their broader applicability, ignoring the specific cost and architectural constraints for S3.

To allow EC2 instances in a private subnet to access Amazon S3 without traversing the public internet, an S3 Gateway Endpoint is the optimal solution. This configuration ensures data remains within the AWS network while minimizing costs compared to other connectivity options.

Common mistake: Candidates often choose Option C (Interface Endpoint) because it provides secure access, but they overlook the 'MOST cost-effectively' requirement. Interface endpoints incur hourly charges and data processing fees, whereas Gateway endpoints are free.

Expert Analysis

Why the Answer Is Correct

Option D is correct because an S3 Gateway Endpoint adds a route in your VPC's route table to direct traffic destined for S3 to the S3 service through the AWS backbone network. This keeps traffic off the public internet, satisfying regulatory requirements. Crucially, Gateway Endpoints are free of charge, making them the most cost-effective solution among the choices provided.

Why the Other Options Are Wrong

Option A (NAT Gateway) allows outbound internet access but does not restrict S3 traffic from going over the public internet unless explicitly routed to an endpoint, and it incurs significant hourly and data processing costs. Option B (Storage Gateway) is for hybrid cloud storage integration, not for securing internal VPC-to-S3 traffic. Option C (Interface Endpoint) uses AWS PrivateLink and ENIs; while it secures traffic, it incurs hourly fees and data processing costs, violating the 'most cost-effective' constraint compared to the free Gateway Endpoint.

Community Comment Notes

The community consensus strongly favors Option D, with multiple users noting that "Gateway endpoint is cheaper than Interface endpoint" and highlighting that gateway endpoints are free. Some learners initially considered Interface endpoints due to granular controls but were corrected on the cost implications. Comments emphasize that since the application is already in AWS, there is no need for the complexity or cost of Interface endpoints when Gateway suffices.

Official Reference

https://docs.aws.amazon.com/vpc/latest/privatelink/vpc-endpoints.html

This link opens the official vendor documentation in a new tab.

Exam Strategy

When asked for the 'most cost-effective' way to connect VPC resources to supported services like S3 or DynamoDB, always prioritize Gateway Endpoints over Interface Endpoints because they are free. Remember that Gateway Endpoints only work for S3 and DynamoDB.

Frequently Asked Questions

Why is an S3 Interface Endpoint not the best choice here?

While Interface Endpoints provide private access, they incur hourly charges and data processing fees. Since the question asks for the MOST cost-effective solution, the free Gateway Endpoint is superior.

Can a NAT Gateway be used to access S3 privately?

A NAT Gateway allows outbound internet access but does not inherently keep S3 traffic off the public internet. Without a VPC endpoint, traffic would still traverse the public internet unless a specific endpoint is configured.

More SAA-C03 FAQ →

Community Votes

D
100%

100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 10 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 10

  1. Scheldon 👍 4 Answered D
    AnswerD https://docs.aws.amazon.com/AmazonS3/latest/userguide/privatelink-interface-endpoints.html taking into consideration that in both cases (s3 Instance Endpoint and S3Gateway endpoint), network traffic remains on the AWS network we need to think about other data which we have. For example application is in AWS cloud hence there is no need for access from on-premises. in that situation S3 Gateway endpoint seems to be better (and it is for free) https://docs.aws.amazon.com/AmazonS3/latest/userguide/privatelink-interface-endpoints.html#types-of-vpc-endpoints-for-s3
  2. KennethNg923 👍 4 Answered D
    Gateway endpoint free, so definitely interface end point expensive than it
  3. awsshare 👍 2 Answered D
    Sorry, I think D is the correct option. Gateway endpoint is cheaper than Interface endpoint
  4. mk168898 👍 2
    no internet and need access to s3 => s3 gateway endpoint
  5. LeonSauveterre 👍 1 Answered D
    About option C - S3 Interface Endpoint 1. Creates a private network interface (ENI) in your VPC that connects to Amazon S3. 2. Provides granular IAM-based controls at the operation level. 3. Typically much more expensive due to the cost associated with the network interface and data processing charges. About option D - S3 Gateway Endpoint: 1. Creates a route entry in the VPC route table for accessing S3 without crossing the public internet. 2. Simpler and more cost-effective for high-volume S3 access, as there are no additional data processing charges or interface costs. 3. Doesn't support granular IAM controls per operation, but bucket policies can be used for access control so that's good.
Show 5 more comments
  1. JA2018 👍 1 Answered C
    Why I opt for Option C? #Private Access: It allows direct access to S3 buckets from a private subnet without data traversing the public internet, meeting the regulatory requirement. #Cost-Effective: Compared to other options, utilizing an S3 interface endpoint is generally the most cost-efficient way to achieve private access to S3. #Summary: When data needs to stay within a private network, use an S3 interface endpoint to access S3 buckets. Always consider the specific regulatory requirements and cost implications when choosing a solution.
  2. Tanidanindo 👍 4 Answered D
    Gateway endpoint for S3
  3. BatVanyo 👍 3 Answered D
    Gateway endpoints are free.
  4. Hkayne 👍 2 Answered D
    D for sure.
  5. awsshare 👍 2 Answered C
    should be C

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