SAA-C03 Design Cost-Optimized Architectures Practice Question
A batch analytics job currently uses two NAT gateways in each of three Availability Zones, but only one private subnet per AZ needs outbound internet access. What should the architect review first? The design must avoid adding custom operational scripts.
⚠ Common exam trap
Test-takers frequently assume more NAT gateways are always better for high availability, but the question explicitly states only one private subnet per AZ needs outbound access, making a single NAT gateway per AZ the cost-optimized starting point.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Whether one NAT gateway per AZ is sufficient for the required private subnets
The current setup uses two NAT gateways per AZ, which is likely over-provisioned and incurs unnecessary costs. Since only one private subnet per AZ requires outbound internet access, a single NAT gateway per AZ is typically sufficient to handle the traffic, and this is the first cost-optimization step to review before making other changes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replacing every NAT gateway with an internet gateway attached to private subnets
Why it's wrong here
An internet gateway (IGW) attaches to a VPC, not directly to subnets, and its default behavior is to provide internet connectivity only to resources that have public IPv4 addresses or are using IPv6. A private subnet's instances typically lack public IPs, so an IGW cannot be used as a direct next hop for them; attempting this forces you to assign public IPs, destroying the private-subnet security model. To enable outbound-only internet access from private subnets, you must route 0.0.0.0/0 to a NAT gateway or NAT instance in a public subnet, not to an IGW.
- ✓
Whether one NAT gateway per AZ is sufficient for the required private subnets
Why this is correct
NAT gateways are provisioned per Availability Zone, and the standard high-availability pattern is one NAT gateway per AZ, not multiple in the same AZ. If the batch analytics job runs in only one AZ or its required private subnets are all within a single AZ, a second NAT gateway in that same AZ provides no additional resilience while doubling the hourly and data-processing charges. The cost optimization is to confirm that each AZ contains at least one private subnet needing egress; if not, the NAT gateway count should be reduced to one per AZ with active private workloads.
- ✗
Disabling route tables
Why it's wrong here
Route tables are mandatory VPC components; every subnet must be associated with a route table, and AWS does not allow you to 'disable' or delete the main route table or the route tables required for the VPC to function. Removing or disabling route tables would break all routing in the private subnets, cutting off the batch job from the NAT gateway, other VPC resources, and any connected services. Cost savings cannot justify eliminating the core routing mechanism, and the correct approach is to review and prune unused route entries rather than disabling the tables themselves.
- ✗
Moving all workloads to public subnets
Why it's wrong here
Placing all batch workloads in public subnets would remove the need for NAT gateways, but this dramatically increases the attack surface, as every instance would receive a public IP and be directly reachable from the internet. It would also require reconfiguring security groups and network ACLs to mitigate exposure, and may incur costs for Elastic IPs if static addresses are needed, making the 'savings' from NAT gateways illusory. Cost optimization must preserve the security architecture's intent—private instances with controlled egress—not shift the workload to an openly exposed environment.
Visual reference
Go deeper
Related to this question
About these practice questions
Courseiva writes every SAA-C03 question from scratch — 935 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAA-C03 exam.