SAA-C03 Design Cost-Optimized Architectures Practice Test 4 — 15 Questions

Question 1

A company runs EC2 workloads in one region with somewhat steady overall demand. Over time, the team frequently changes instance families (for performance/optimization) and sometimes changes instance size, but wants predictable cost discounts. Which purchase option provides the best balance of cost savings and flexibility?

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

Accepted Answer

Savings Plans (Compute Savings Plans), scoped for flexible EC2 usage in the region.. Compute Savings Plans offer the best balance of cost savings and flexibility because they provide up to 66% discount in exchange for a commitment to a consistent amount of compute usage (measured per hour) in a region, but they automatically apply to any EC2 instance family, size, OS, or tenancy, as well as AWS Fargate and Lambda. This matches the team's need to frequently change instance families and sizes while still getting predictable discounts, unlike Standard RIs which lock you to a specific family and size.

Answer

Standard Reserved Instances for a specific instance family and size only.

Answer

Spot Instances for all workloads, assuming interruptions will never happen.

Answer

On-Demand only, because it avoids the complexity of purchase option scopes.

Question 2

A video processing pipeline runs batch jobs that are safe to interrupt and restart. The jobs checkpoint progress to durable storage every few minutes, and the team can automatically resubmit from the last checkpoint. They want to minimize compute cost while accepting that capacity can be interrupted. Which launch configuration for the processing workers is the best cost-optimized choice?

Accepted Answer

Launch the worker nodes as Spot Instances, and configure the job resubmission logic to restart from checkpoints upon interruption.. Spot Instances offer significant cost savings (up to 90% compared to On-Demand) and are ideal for fault-tolerant, interruptible workloads. Since the pipeline checkpoints progress to durable storage and can automatically resume from the last checkpoint, using Spot Instances minimizes compute cost while accepting interruptions.

Answer

Launch the worker nodes as On-Demand Instances with no interruption handling so the pipeline never needs resubmission.

Answer

Launch the worker nodes as Reserved Instances to guarantee capacity and reduce cost, ignoring interruptions.

Answer

Use Savings Plans and also set the job scheduler to never start new jobs unless previous jobs finish without interruption.

Question 3

A team serves static web assets (JS, CSS, images) from an Amazon S3 origin through CloudFront. Recently, the S3 origin has received a high number of requests for the same files, increasing origin data transfer costs. CloudFront access logs show many cache misses, and each request includes a unique query string used only for tracking (for example, ?utm=...). The application does not require query-string-specific content. What CloudFront change will most directly reduce origin fetches and cost?

Accepted Answer

Update the CloudFront cache policy to exclude query strings from the cache key so that requests differing only by tracking query parameters reuse the same cached object.. CloudFront's cache policy controls which parts of a request (including query strings) are included in the cache key. By excluding the tracking query strings (e.g., `?utm=...`) from the cache key, CloudFront will treat all requests for the same file as identical, serving the cached object regardless of the query string. This directly reduces the number of origin fetches (cache misses) and lowers S3 data transfer costs, as the application does not require query-string-specific content.

Answer

Lower the minimum TTL and set Cache-Control headers to no-store to force CloudFront to revalidate more often.

Answer

Enable Origin Shield to ensure all origin fetches go through a single regional shield with no other configuration changes.

Answer

Switch the S3 origin from S3 to a different storage class optimized for request rates, keeping the cache key the same.

Question 4

A startup runs a mix of workloads using both EC2 instances and AWS Lambda functions. Over the next 12 months, the team expects the overall level of compute usage to be fairly steady, but they may change EC2 instance types for performance tuning and they may add or remove Lambda functions. They want the lowest-cost commitment that will discount *both* EC2 and Lambda usage without requiring them to commit to a specific EC2 instance family (or a fixed instance type). Which AWS option best meets this requirement?

Accepted Answer

Purchase a Compute Savings Plan with a 1-year term for the expected average hourly spend across both EC2 and Lambda.. B is correct because a Compute Savings Plan offers the lowest cost commitment that covers both EC2 and Lambda usage, with flexibility to change instance families, sizes, regions (within the same AWS organization), and even switch between EC2 and Fargate. It applies a consistent hourly discount to compute usage up to the committed amount, regardless of instance type or compute service, meeting the startup's need for a steady workload with potential changes.

Answer

Purchase an EC2 Instance Reserved Instance for the current instance family only, and rely on On-Demand pricing for Lambda and any future EC2 types.

Answer

Purchase a Standard Reserved Instance for a specific Region and use it only to reduce network egress/transfer charges.

Answer

Use EC2 Spot for EC2 workloads and keep Lambda on-demand, because Spot will automatically discount Lambda too.

Question 5

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?

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 6

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 7

An ecommerce company runs a 24/7 frontend tier on EC2 and a nightly image-rendering job that can be interrupted and resumed from checkpoints. They want to minimize monthly compute cost without changing the application architecture. Which two actions should they take? Select two.

Accepted Answer

Purchase a Compute Savings Plan for the always-on frontend tier.. A Compute Savings Plan offers the largest discount (up to 66%) in exchange for a consistent compute spend commitment, making it ideal for the always-on frontend tier that runs 24/7. This plan applies to any EC2 instance family, region, and even Fargate or Lambda, providing flexibility while reducing costs for steady-state workloads.

Answer

Move both workloads to Dedicated Hosts.

Answer

Keep the rendering fleet entirely on On-Demand Instances.

Answer

Use dedicated GPUs for the frontend tier even though it is CPU-light.

Question 8

A media company stores application logs in S3. The logs must be kept for 400 days. They are read heavily for the first 30 days, occasionally for the next 90 days, and almost never after that. Retrieval after the first 3 months can wait a few hours. Which three lifecycle actions should they use to minimize storage cost? Select three.

Accepted Answer

Transition objects to S3 Standard-IA after 30 days.. After the initial 30-day period of heavy reads, transitioning objects to S3 Standard-IA reduces storage costs while still providing low-latency retrieval for the occasional access needed over the next 90 days. S3 Standard-IA is designed for data accessed infrequently but requires rapid access when needed, making it cost-effective for this usage pattern.

Answer

Keep all objects in S3 Standard for the full retention period.

Answer

Transition objects to S3 One Zone-IA after 30 days.

Question 9

An application runs in private subnets and must access Amazon S3, Amazon DynamoDB, and AWS Secrets Manager. The security team wants the traffic to stay on the AWS network and the finance team wants to eliminate NAT Gateway charges. Which three changes should they make? Select three.

Accepted Answer

Create gateway VPC endpoints for S3.. A gateway VPC endpoint for S3 allows instances in private subnets to access S3 over the AWS network without traversing the internet or a NAT gateway. This eliminates NAT Gateway charges and keeps traffic on the AWS backbone, meeting both security and cost requirements.

Answer

Place the instances in public subnets with an internet gateway.

Answer

Keep the NAT Gateway and add a proxy instance for service access.

Question 10

A static site is hosted in Amazon S3 and delivered by CloudFront. After a frontend release, the same JavaScript bundles are fetched repeatedly from the origin. Logs show that requests include unneeded query strings and cookies, which prevent cache reuse. Which two changes should the team make to reduce origin traffic and cost? Select two.

Accepted Answer

Configure a CloudFront cache policy that forwards only the query strings, headers, and cookies the app actually needs.. CloudFront cache policies allow you to explicitly control which query strings, headers, and cookies are forwarded to the origin. By forwarding only the parameters the application actually needs, you prevent cache keys from being polluted by unneeded values, which increases the cache hit ratio and reduces requests to the S3 origin. This directly addresses the problem of repeated fetches caused by extraneous query strings and cookies.

Answer

Increase the size of the S3 bucket.

Answer

Place an Application Load Balancer in front of S3.

Answer

Disable caching so clients always get the latest files.

Question 11

A public API currently uses API Gateway REST APIs and Lambda. Traffic is low most of the day, but marketing runs a predictable traffic spike every weekday at 09:00 UTC. Users complain about cold starts during the first few minutes of the spike, and the team wants to avoid paying for provisioned concurrency all day. Which two changes should they make? Select two.

Accepted Answer

Switch from REST APIs to HTTP APIs if the feature set is sufficient.. HTTP APIs are designed to be faster and more cost-effective than REST APIs, with up to 71% lower latency and 60% lower cost per request. This reduces the impact of cold starts by minimizing the overhead of request processing, and the cost savings align with the team's goal of avoiding all-day provisioned concurrency costs.

Answer

Keep provisioned concurrency at the maximum level 24/7.

Answer

Move the API to a single t3.nano EC2 instance.

Answer

Add an S3 gateway endpoint to reduce cold starts.

Question 12

A development team stores application logs in CloudWatch Logs and has enabled detailed EC2 monitoring on every instance. Auditors only require 90 days of logs, and operations only needs 5-minute instance metrics. Which three changes would most directly reduce recurring monitoring costs while still meeting those requirements? Select three.

Accepted Answer

Set CloudWatch Logs retention to 90 days.. Setting CloudWatch Logs retention to 90 days ensures logs are automatically deleted after the required period, eliminating storage costs for older data. By default, logs never expire, which would incur ongoing charges for data beyond the audit requirement. This directly reduces recurring costs by limiting the log data stored.

Answer

Keep CloudWatch Logs retention set to Never Expire.

Answer

Enable high-resolution custom metrics for every request.

Question 13

An application team sees that a fleet of EC2 instances averages 15% CPU utilization and has no memory pressure. The service must keep running continuously, but the team wants to lower cost with minimal risk. Which two actions should they take first? Select two.

Accepted Answer

Use Compute Optimizer recommendations to identify a smaller instance type.. AWS Compute Optimizer analyzes historical utilization metrics (CPU, memory, network) and provides rightsizing recommendations. Since the fleet averages only 15% CPU with no memory pressure, downsizing to a smaller instance type reduces cost without impacting performance. This is the first step to identify the optimal instance family and size.

Answer

Move the workload to Dedicated Hosts.

Answer

Add a second NAT Gateway.

Answer

Enable Provisioned Concurrency for the EC2 workload.

Question 14

A company runs an order system on EC2 with a self-managed PostgreSQL database, a self-managed RabbitMQ broker, and a shared file server for attachments. The team wants to reduce patching, backups, and cluster administration while keeping the architecture simple and using managed services where possible. Which three changes should they make? Select three.

Accepted Answer

Replace the database with Amazon RDS for PostgreSQL.. Amazon RDS for PostgreSQL is a managed database service that automates patching, backups, and replication, eliminating the need for self-managing PostgreSQL on EC2. This directly reduces the operational overhead of cluster administration and aligns with the goal of using managed services.

Answer

Keep the database on EC2 and add more EBS volumes.

Answer

Move RabbitMQ to Dedicated Hosts for better isolation.

Question 15

A data-processing application runs in private subnets and needs to read objects from Amazon S3 and write items to Amazon DynamoDB. The team currently routes all outbound traffic through a NAT Gateway, and monthly networking charges are rising. Which two changes will most directly reduce cost while keeping traffic on the AWS network? Select two.

Accepted Answer

Add an S3 gateway VPC endpoint to the private route tables.. Adding an S3 gateway VPC endpoint allows instances in private subnets to access S3 directly over the AWS network without traversing the NAT Gateway, eliminating NAT data processing charges for S3 traffic. This reduces monthly networking costs while keeping traffic within the AWS backbone.

Answer

Add a second NAT Gateway in another Availability Zone.

Answer

Move the instances into public subnets so they can reach AWS services directly.

Answer

Send private subnet traffic to S3 and DynamoDB through an Internet Gateway route.