SAA-C03 Design Cost-Optimized Architectures Practice Test 9 — 15 Questions

Question 1

An Auto Scaling group for a background worker runs EC2 instances continuously. Over the last 30 days, CloudWatch shows sustained CPU utilization around 6% with no memory pressure, and queue processing latency meets all SLAs. The team wants to lower monthly cost with minimal risk. What is the best next action?

Accepted Answer

Perform right sizing by downsizing to a smaller instance family/size and validate SLAs. The current instance type is over-provisioned, as sustained CPU utilization is only 6% with no memory pressure and all SLAs are met. Right-sizing to a smaller instance family or size directly reduces compute cost while maintaining performance, making it the lowest-risk, cost-optimization action. This aligns with the AWS Well-Architected Framework's cost optimization pillar, which recommends matching instance capacity to actual workload requirements.

Answer

Increase the instance size to reduce CPU throttling risk

Answer

Switch the group to Spot Instances to reduce cost without changing instance sizing

Answer

Buy Reserved Instances with a long term commitment before making any sizing changes

Question 2

A company hosts application servers in private subnets. They must access Amazon S3 and read secrets from AWS Secrets Manager, but they want to avoid internet egress. They currently use a NAT gateway and see high NAT-related costs. What change most directly reduces cost while keeping traffic on the AWS network?

Accepted Answer

Create a Gateway VPC endpoint for S3 and an Interface VPC endpoint for Secrets Manager, then route requests via those endpoints instead of NAT. Option B is correct because it replaces the NAT gateway with VPC endpoints, which are free of data processing charges and keep all traffic within the AWS network. A Gateway VPC endpoint for S3 uses prefix lists and route table entries to send S3 traffic directly over the AWS backbone, while an Interface VPC endpoint for Secrets Manager uses AWS PrivateLink to provide private connectivity without internet egress. This eliminates NAT gateway hourly and data processing costs, directly addressing the cost concern.

Answer

Keep the NAT gateway and reduce instance size to lower NAT throughput charges

Answer

Switch Secrets Manager to use S3 as a storage backend so both services can use the S3 endpoint only

Answer

Move the private subnets to public subnets and attach an Internet Gateway to eliminate NAT

Question 3

A team runs an EC2-based service and ships logs to Amazon CloudWatch Logs. They enabled long log retention and turned on detailed monitoring to improve troubleshooting. Their monthly CloudWatch costs have grown unexpectedly. Compliance requires that the logs remain available in CloudWatch Logs (for querying and audits) for 90 days, and alerts/alarms do not require detailed EC2 monitoring. What change best reduces cost while meeting requirements?

Accepted Answer

Set the CloudWatch Logs retention to 90 days and disable detailed EC2 monitoring (use standard monitoring) for the instances. Option B reduces costs by setting CloudWatch Logs retention to exactly 90 days (meeting compliance) and disabling detailed monitoring (which incurs per-minute metrics charges) in favor of standard 5-minute monitoring. This directly addresses the two main cost drivers—long retention and detailed EC2 monitoring—while preserving the required 90-day log availability for queries and audits.

Answer

Keep the current long retention and detailed monitoring; reduce the log volume by sampling 10% of events

Answer

Move all logs to S3 immediately and delete the CloudWatch log groups to reduce costs

Answer

Increase CloudWatch alarm thresholds to reduce the number of metric datapoints

Question 4

A batch analytics job runs for several hours each night and can be interrupted and restarted. Which EC2 purchasing option should minimize cost?

Accepted Answer

Spot Instances. Spot Instances are the correct choice because they offer significant cost savings (up to 90% compared to On-Demand) and are ideal for fault-tolerant, interruptible workloads like batch processing. Since the job can be interrupted and restarted, it can handle Spot Instance terminations gracefully, making this the most cost-effective option.

Answer

On-Demand Instances only

Answer

Dedicated Hosts

Answer

Provisioned IOPS volumes

Question 5

A production internal reporting portal runs continuously on EC2 with predictable usage for the next three years. The team wants a discount while retaining some instance-family flexibility. What should they buy?

Accepted Answer

Compute Savings Plan. A Compute Savings Plan offers the lowest prices on EC2 usage (up to 66% off On-Demand) in exchange for a 1- or 3-year commitment, and it automatically applies to any EC2 instance family in any region, giving the flexibility the team needs. Since the workload runs continuously with predictable usage for three years, this plan is ideal for reducing costs while retaining the ability to change instance families if needed.

Answer

Spot Instances only

Answer

Dedicated Instances

Answer

S3 Intelligent-Tiering

Question 6

A test environment stores logs in S3. Logs are queried for 30 days, rarely accessed for one year, and then retained for compliance. What should reduce storage cost?

Accepted Answer

S3 lifecycle policy that transitions objects to lower-cost storage classes over time. Option C is correct because an S3 Lifecycle policy automates the transition of objects from S3 Standard (for frequent access) to S3 Standard-IA (infrequent access) after 30 days, then to S3 Glacier Deep Archive (for long-term retention) after one year, minimizing storage costs while maintaining data accessibility as needed.

Answer

Keep all logs in S3 Standard indefinitely

Answer

Move all logs immediately to S3 Glacier Deep Archive

Answer

Use EBS snapshots for the logs

Question 7

A media processing workflow in private subnets downloads large amounts of data from S3 through a NAT gateway. NAT data processing charges are high. What should the architect use to reduce cost?

Accepted Answer

Gateway VPC endpoint for Amazon S3. A Gateway VPC endpoint for Amazon S3 allows instances in private subnets to access S3 directly via the AWS network without traversing a NAT gateway, eliminating NAT data processing charges. This is the most cost-effective solution because NAT gateway costs are incurred per GB of data processed, and using a gateway endpoint avoids those charges entirely.

Answer

S3 Object Lambda

Answer

AWS Shield Advanced

Answer

A larger NAT gateway

Question 8

A dev sandbox has unpredictable DynamoDB traffic with long idle periods and occasional spikes. Which capacity mode should minimize operational overhead and avoid paying for idle provisioned capacity?

Accepted Answer

DynamoDB on-demand capacity mode. DynamoDB on-demand capacity mode (Option C) is ideal for unpredictable workloads with long idle periods and occasional spikes because it automatically scales to handle traffic without requiring any capacity planning. You pay only for the reads and writes you actually perform, eliminating the cost of idle provisioned capacity and the operational overhead of managing scaling.

Answer

Reserved capacity for maximum daily traffic

Answer

Provisioned capacity set for peak traffic

Answer

Global tables in every Region

Question 9

A log archive has old unattached EBS volumes and many stale snapshots. Which two actions reduce storage cost without affecting running instances?

Accepted Answer

Delete unattached EBS volumes after verifying they are no longer needed. Unattached EBS volumes incur storage costs even when not in use, as EBS pricing is based on provisioned capacity per GB-month. Deleting them after verifying they are no longer needed eliminates this cost without affecting running instances, since attached volumes are untouched. This directly addresses the question's requirement to reduce storage costs without impacting running workloads.

Answer

Stop all EC2 instances in the account

Answer

Disable CloudTrail logging

Question 10

A marketing site runs on x86 EC2 instances and uses open-source software with no architecture-specific licensing restriction. What should be evaluated to reduce compute cost?

Accepted Answer

AWS Graviton-based instances after performance testing. Option C is correct because AWS Graviton-based instances (ARM architecture) offer up to 40% better price-performance compared to comparable x86 instances for many workloads. Since the marketing site uses open-source software with no architecture-specific licensing restrictions, migrating to Graviton after performance testing can significantly reduce compute costs without sacrificing performance.

Answer

Cross-Region data replication for all data

Answer

io2 Block Express volumes for all instances

Answer

Dedicated Hosts by default

Question 11

A risk simulation workload uses CloudWatch Logs heavily. Retaining all debug logs forever is increasing costs. What should be configured?

Accepted Answer

CloudWatch Logs retention policies per log group. CloudWatch Logs retention policies allow you to set per-log-group expiration rules (e.g., 30 days, 90 days) to automatically delete old log events, directly reducing storage costs for debug logs that are no longer needed. This is the most cost-effective and targeted solution for managing log lifecycle without affecting other monitoring or configuration services.

Answer

AWS Config aggregation

Answer

CloudWatch detailed monitoring on all instances

Answer

Route 53 health checks

Question 12

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?

Accepted Answer

Whether one NAT gateway per AZ is sufficient for the required private subnets. Option B is correct because the question asks what the architect should review first. Using two NAT gateways per Availability Zone (AZ) when only one private subnet per AZ needs outbound internet access is likely over-provisioned and costly. The architect should first verify if a single NAT gateway per AZ can handle the traffic load, as NAT gateways are highly available within an AZ and can support up to 45 Gbps of bandwidth. This review directly addresses cost optimization without sacrificing functionality.

Answer

Replacing every NAT gateway with an internet gateway attached to private subnets

Answer

Disabling route tables

Answer

Moving all workloads to public subnets

Question 13

A internal reporting portal serves infrequently accessed user documents that must be available immediately when requested. Which S3 storage class is likely the best cost fit?

Accepted Answer

S3 Standard-IA or S3 One Zone-IA depending on resilience requirements. S3 Standard-IA or S3 One Zone-IA is the best cost fit because the data is infrequently accessed but must be available immediately when requested. These storage classes offer low-latency retrieval (milliseconds) at a lower storage cost than S3 Standard, with the trade-off of a retrieval fee. The choice between Standard-IA and One Zone-IA depends on whether the application requires resilience against Availability Zone failures.

Answer

Instance store volumes

Answer

S3 Glacier Deep Archive

Answer

S3 Standard for all objects

Question 14

A test environment has EC2 instances that are oversized based on CPU, memory, and network utilisation. Which AWS service should identify rightsizing recommendations?

Accepted Answer

AWS Compute Optimizer. AWS Compute Optimizer uses machine learning to analyze historical utilization metrics (CPU, memory, network, and storage) and provides rightsizing recommendations for EC2 instances, including over-provisioned resources. It helps reduce costs by suggesting instance types or sizes that better match actual workload demands.

Answer

AWS DataSync

Answer

AWS Shield

Answer

AWS Artifact

Question 15

A media processing workflow generates analytics files that are accessed unpredictably. Some files become hot again months later. The team wants automatic storage cost optimisation without retrieval delays. What should be used?

Accepted Answer

S3 Intelligent-Tiering. S3 Intelligent-Tiering automatically moves objects between access tiers (frequent, infrequent, and archive instant access) based on changing access patterns, with no retrieval delays for hot objects. This is ideal for unpredictable access where some files become hot again months later, as it optimizes storage costs without manual intervention or retrieval latency.

Answer

Manual monthly review and object copying

Answer

S3 Glacier Flexible Retrieval for all files

Answer

EFS One Zone for analytics files