SAA-C03 Design Cost-Optimized Architectures Practice Test 11 — 15 Questions

Question 1

A company serves versioned images from S3 through CloudFront. After a release, CloudFront origin fetches increased sharply and the monthly CloudFront bill went up. They reviewed CloudFront logs and found that many requests include a query string parameter `reqId` that is unique per request (for example, `...?v=2026-04-01&reqId=...`). The team currently forwards all query strings to the cache key. What change is most likely to reduce origin fetches and cost while keeping the versioned images correct?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Update the CloudFront cache policy to ignore `reqId` and include only the stable `v` query string parameter in the cache key.. The `reqId` query string parameter is unique per request, which forces CloudFront to treat each request as a distinct cache object when all query strings are forwarded to the cache key. By configuring the cache policy to include only the stable `v` parameter (the version identifier) and ignore `reqId`, CloudFront can serve cached responses for all requests with the same `v` value, drastically reducing origin fetches and lowering costs. This approach preserves correct versioned image delivery because the `v` parameter still differentiates between image versions.

Answer

Lower the CloudFront minimum TTL to 0 seconds so cached objects revalidate more often, reducing origin fetch volume.

Answer

Set the S3 bucket to use compression and enable S3 Transfer Acceleration to reduce origin fetch charges.

Answer

Disable forwarding of the query string to the origin, but keep using the full query string (including `reqId`) in the cache key.

Question 2

A team runs an EC2-based API on a single Auto Scaling group (ASG). Over the last month, they observed: - Average CPU utilization is ~15%. - p95 latency is stable and within the performance target. - The attached EBS volumes are gp3, provisioned with high baseline IOPS/throughput “just to be safe,” but CloudWatch shows consistently low utilization of those provisioned IOPS/throughput limits. They want to reduce monthly cost while maintaining current performance. Which action is the best cost-optimized choice?

Accepted Answer

Right-size both the compute and the gp3 volumes: reduce the EC2 instance size (via the ASG launch template/desired capacity configuration) and update gp3 IOPS/throughput settings to match observed utilization while keeping p95 latency targets.. The workload is over-provisioned in both compute and storage. Average CPU is only 15%, so a smaller instance size can handle the load without affecting p95 latency. The gp3 volumes have high baseline IOPS/throughput that are never used, so reducing them to match actual utilization directly lowers costs without performance risk.

Answer

Stop resizing EBS and only scale out the ASG during peak traffic, because changing EBS performance settings risks latency spikes.

Answer

Switch the instances to EC2 Spot immediately, because Spot always lowers costs without adding operational risk or affecting performance.

Answer

Move the workload to a larger instance class and keep the gp3 settings unchanged to avoid operational tuning work.

Question 3

A startup runs a 24/7 web tier on Amazon EC2 with a stable baseline of 8 instances and a nightly analytics batch job that can resume from checkpoints if interrupted. The company wants to minimize monthly compute cost without hurting the always-on web tier. Which two actions should it take? Select two.

Accepted Answer

Buy a Compute Savings Plan for the steady web tier baseline.. A Compute Savings Plan offers the largest discount (up to 66%) in exchange for a 1- or 3-year hourly spend commitment, and it automatically applies to any EC2 instance family, size, or region. For the stable 8-instance web tier that runs 24/7, this plan provides significant cost savings while maintaining full flexibility to change instance types or even move to containers or Lambda, without affecting the always-on requirement.

Answer

Buy Standard Reserved Instances only for the nightly analytics batch job.

Answer

Move the entire workload to On-Demand Instances for maximum flexibility.

Answer

Use Dedicated Hosts for the batch job so the fleet is isolated.

Question 4

Based on the exhibit, your application runs entirely in private subnets and only needs to reach Amazon S3, Amazon DynamoDB, AWS Secrets Manager, and CloudWatch Logs. The monthly bill is dominated by NAT Gateway charges. Which change most directly reduces cost while preserving private connectivity to these AWS services?

Accepted Answer

Create S3 and DynamoDB gateway endpoints, create interface endpoints for Secrets Manager and CloudWatch Logs, update route tables, and remove the NAT Gateway.. It replaces the costly NAT Gateway with free VPC Gateway Endpoints for S3 and DynamoDB, and uses AWS PrivateLink interface endpoints for Secrets Manager and CloudWatch Logs. This eliminates all internet-bound data transfer costs while keeping traffic entirely within the AWS network, directly addressing the cost concern without sacrificing private connectivity.

Answer

Replace the NAT Gateway with an Internet Gateway and keep the current private subnet routes unchanged.

Answer

Add a second NAT Gateway in another Availability Zone to reduce cross-AZ data transfer charges.

Answer

Create only interface endpoints for all four services and keep the NAT Gateway for fallback.

Question 5

Based on the exhibit, the team wants to minimize compute cost for a workload with a steady 24/7 baseline and a separate nightly batch job that can be interrupted and resumed from checkpoints. They also expect to change EC2 instance families during the year as performance needs evolve. Which approach is the best fit?

Accepted Answer

Use a Compute Savings Plan to cover the steady baseline and run the nightly batch on Spot Instances.. A Compute Savings Plan covers any EC2 instance family (or even container/Fargate usage) at a discounted rate, making it ideal for the steady 24/7 baseline. The nightly batch job can be interrupted and resumed from checkpoints, which is a perfect use case for Spot Instances, offering up to 90% cost savings. This combination minimizes compute cost while maintaining flexibility to change instance families during the year.

Answer

Buy EC2 Instance Savings Plans for the baseline and run the nightly batch on On-Demand instances.

Answer

Purchase Standard Reserved Instances for all 12 instances and keep the current families fixed.

Answer

Run both tiers entirely on Spot Instances and rely on automatic restarts for the baseline web tier.

Question 6

Based on the exhibit, the company stores application logs in Amazon S3 for 400 days. The logs are read heavily for the first 30 days, occasionally for the next 90 days, and very rarely after that. Retrieval after day 120 can take up to several hours, but the data must remain available until day 400. Which lifecycle policy is the most cost-effective fit?

Accepted Answer

Transition logs to S3 Standard-IA after 30 days, then to S3 Glacier Flexible Retrieval after 120 days, and expire them at 400 days.. It aligns the storage class transitions with the access patterns: S3 Standard for the first 30 days (heavy reads), S3 Standard-IA for the next 90 days (occasional reads), and S3 Glacier Flexible Retrieval for the remaining period (rare access, with retrieval up to several hours acceptable). This minimizes storage costs while ensuring data availability until day 400, where lifecycle expiration removes the objects.

Answer

Keep all logs in S3 Standard for 400 days and enable requester pays to reduce the company's bill.

Answer

Transition logs directly from S3 Standard to S3 Glacier Deep Archive after 30 days and expire them at 400 days.

Answer

Move logs to S3 Intelligent-Tiering only and disable lifecycle transitions because access is unpredictable.

Question 7

Based on the exhibit, the team serves versioned JavaScript and CSS files from an S3 origin through CloudFront. After a release, the cache hit ratio dropped and origin fetches increased sharply. What change best reduces both CloudFront and S3 costs without changing the application’s public behavior?

Accepted Answer

Create a cache policy that excludes Authorization, cookies, and unnecessary query strings, and narrow the origin request policy to forward only the headers the S3 origin actually needs.. B is correct because versioned JavaScript and CSS files are immutable, so CloudFront should cache them aggressively. By creating a cache policy that excludes unnecessary headers (like Authorization and cookies) and query strings, and narrowing the origin request policy to forward only required headers, you maximize cache hits and reduce origin fetches. This directly lowers both CloudFront data transfer costs (fewer origin requests) and S3 request costs (fewer GET requests), without altering the application's public behavior.

Answer

Increase the CloudFront price class to include more edge locations.

Answer

Disable CloudFront and serve the files directly from S3 to avoid cache invalidation overhead.

Answer

Use Lambda@Edge to rewrite every request into a unique path so that clients never receive stale files.

Question 8

Based on the exhibit, the company wants to lower CloudWatch and EC2 monitoring costs. Auditors require logs to be retained for 90 days, but operations only uses detailed per-instance metrics during rare troubleshooting events. Which change best reduces recurring cost while preserving the required visibility?

Accepted Answer

Set CloudWatch Logs retention to 90 days for all log groups, and switch EC2 monitoring from detailed to basic except during incidents.. It directly addresses the two cost drivers: CloudWatch Logs storage costs are minimized by setting a 90-day retention policy (matching the audit requirement), and EC2 detailed monitoring (1-minute metrics) is replaced with basic monitoring (5-minute metrics) during normal operations, with the ability to switch back to detailed only when needed for troubleshooting. This preserves the required log retention and the ability to obtain high-resolution metrics on demand, while eliminating the recurring cost of storing logs indefinitely and paying for detailed monitoring on every instance.

Answer

Disable CloudWatch Logs entirely and rely on application local files for 90 days.

Answer

Increase the number of CloudWatch alarms so that metrics are collected less expensively.

Answer

Export all logs to Amazon S3 immediately and keep detailed monitoring enabled on every instance.

Question 9

Based on the exhibit, the company runs a self-managed RabbitMQ cluster on EC2 for asynchronous work. The queue only needs durable at-least-once delivery, and the application does not require AMQP-specific features such as exchanges, routing keys, or broker plugins. Which change is the best cost-optimization move?

Accepted Answer

Replace RabbitMQ with Amazon SQS Standard and keep the workers unchanged except for the queue client library.. Amazon SQS Standard provides at-least-once delivery and durable message storage without requiring AMQP-specific features like exchanges or routing keys. Replacing RabbitMQ with SQS eliminates the operational overhead of managing EC2 instances and RabbitMQ clusters, while SQS's pay-per-request pricing is more cost-effective than running EC2 instances 24/7 for a self-managed queue.

Answer

Replace RabbitMQ with Amazon MQ for RabbitMQ to keep the same protocol and reduce costs.

Answer

Increase the RabbitMQ instance size and add a fourth node for higher availability.

Answer

Move the queue to Amazon DynamoDB and use scans for consumers to detect new messages.

Question 10

An S3 bucket stores application logs. After 30 days, the team rarely accesses the logs, but compliance requires keeping them for 18 months. Which setup most directly reduces storage cost while maintaining compliance?

Accepted Answer

Configure an S3 Lifecycle policy to transition objects to a colder storage class after 30 days and expire (delete) them after 18 months.. S3 Lifecycle policies allow you to automatically transition objects to cheaper storage classes (e.g., S3 Standard-IA or S3 Glacier Deep Archive) after 30 days, reducing storage costs for rarely accessed logs. The policy also sets an expiration action to delete objects after 18 months, meeting the compliance requirement without manual intervention.

Answer

Enable S3 Versioning and rely on deleting old versions after 30 days to reduce storage costs while keeping the latest data.

Answer

Move the bucket to a different AWS region farther from the users to reduce the likelihood of accidental reads and thereby lower storage costs.

Answer

Switch all objects to S3 Glacier Instant Retrieval immediately, regardless of object age, to minimize storage charges.

Question 11

A startup expects steady compute usage around the clock for the next year. They want to reduce costs compared to On-Demand pricing, without tightly planning specific instance types. Which option best matches their goal?

Accepted Answer

Purchase a Compute Savings Plan to receive discounted rates for a usage amount over a 1-year term.. A Compute Savings Plan offers the lowest prices on EC2 compute usage (including Fargate and Lambda) in exchange for a commitment to a consistent amount of compute (measured in $/hour) over a 1-year or 3-year term. This matches the startup's steady, predictable usage and provides up to 66% savings over On-Demand, while allowing flexibility to change instance families, sizes, regions, or even switch to containers without renegotiating the plan.

Answer

Purchase a Reserved Instance that must be tied to exactly one specific instance size (no flexibility to switch instance families).

Answer

Only use Spot Instances and set the workload to stop immediately if capacity is interrupted.

Answer

Rely on On-Demand pricing and add more alarms to detect when costs spike.

Question 12

An application runs on an EC2 Auto Scaling group. Over the last month, CPU utilization averaged 8% with no sustained memory pressure, and response times are stable. The team wants to lower monthly cost without changing the application. What is the most appropriate next step for cost optimization?

Accepted Answer

Evaluate a smaller EC2 instance type (via the Auto Scaling launch template/configuration) for the group and validate performance metrics after the change.. The application is over-provisioned: CPU utilization averages only 8% with no memory pressure and stable response times. By selecting a smaller EC2 instance type in the Auto Scaling launch template or configuration, you directly reduce the per-instance cost while maintaining adequate performance. This is the most straightforward cost optimization step without modifying the application code or architecture.

Answer

Increase desired capacity to 2x so utilization increases and instances become “more efficient.”

Answer

Disable Auto Scaling so the group never scales down to preserve baseline performance.

Answer

Switch the workload to Spot instances immediately to avoid On-Demand charges, regardless of interruption risk.

Question 13

A team stores application logs in Amazon CloudWatch Logs. They enabled long retention and detailed dashboards, resulting in higher-than-expected monthly spend. Compliance requires retaining logs for 90 days, but operations only needs aggregated views. Which change most directly reduces CloudWatch Logs cost while meeting the requirement?

Accepted Answer

Set the CloudWatch Logs log group retention period to 90 days for the relevant log groups.. Setting the CloudWatch Logs log group retention period to 90 days directly reduces storage costs by automatically expiring logs after the compliance-required duration. This eliminates the cost of storing logs beyond 90 days, which was the primary driver of the higher-than-expected spend, while still retaining the data for the mandated period and allowing aggregated views via dashboards.

Answer

Disable VPC flow logs so the applications stop producing logs automatically.

Answer

Increase the logging level to DEBUG to reduce the number of log events by batching them.

Answer

Turn off CloudWatch alarms so logs stop being ingested into CloudWatch Logs.

Question 14

A website serves versioned JavaScript and CSS files through CloudFront, but origin fetches are still high and the CloudFront bill increased. Developers confirm that URLs include a version in the filename (for example, app.1.4.2.js). What CloudFront behavior/configuration is most likely to reduce origin fetches and associated costs?

Accepted Answer

Set long cache headers (for example, Cache-Control: max-age and immutable) on those versioned assets so CloudFront caches them longer.. Setting long cache headers like `Cache-Control: max-age=31536000, immutable` on versioned assets tells CloudFront to cache these objects at edge locations for an extended period. Since the filename changes with each new version, CloudFront treats each version as a unique object and will not re-fetch the old version from the origin, dramatically reducing origin fetches and associated costs.

Answer

Disable compression to reduce CPU time spent at the edge and therefore reduce total cost.

Answer

Lower the cache policy TTLs so clients always get the newest assets quickly.

Answer

Remove version identifiers from filenames so CloudFront caches fewer unique objects.

Question 15

A SaaS company runs a production API on an EC2 Auto Scaling group with steady demand 24/7. The team uses multiple instance types over time (they switch types during tuning) but the overall compute hours are stable. They want a cost reduction without committing to a specific instance type or size. Which AWS pricing option best meets the requirement?

Accepted Answer

Purchase a Compute Savings Plan for the region and commit to a dollar-per-hour amount. B is correct because a Compute Savings Plan provides the flexibility to change instance types, sizes, and even compute services (e.g., EC2, Fargate, Lambda) within a region while still receiving discounted rates (up to 66% vs. on-demand). This matches the requirement of reducing costs without committing to a specific instance type or size, as the plan is based on a dollar-per-hour commitment rather than instance family or tenancy.

Answer

Buy EC2 Spot Instances for the Auto Scaling group to maximize savings

Answer

Purchase Reserved Instances that are limited to a single specific instance type in the Auto Scaling group

Answer

Use on-demand only, and rely on Auto Scaling to reduce cost during low utilization