SAA-C03 Design Cost-Optimized Architectures Practice Test 6 — 15 Questions

Question 1

A latency-sensitive API is implemented with AWS Lambda. The team enabled provisioned concurrency to avoid cold starts, setting provisioned concurrency to 50 because marketing campaigns occasionally cause spikes. However, during most weekdays the API receives little traffic (near zero), and the team is seeing high monthly Lambda costs from idle provisioned capacity. What is the best cost-optimized strategy that still meets the requirement of fast initial responses during traffic spikes?

Accepted Answer

Use Application Auto Scaling scheduled actions to increase provisioned concurrency on the Lambda alias before campaign windows and reduce it to a minimal baseline afterward.. Option B is correct because it uses Application Auto Scaling scheduled actions to dynamically adjust provisioned concurrency, scaling up to 50 before marketing campaigns and reducing to a minimal baseline (e.g., 1-5) during low-traffic weekdays. This eliminates idle capacity costs while ensuring fast initial responses during spikes, as provisioned concurrency keeps Lambda environments warm and ready to handle requests without cold starts.

Answer

Increase provisioned concurrency to 100 so that cold starts never occur, regardless of traffic patterns.

Answer

Turn provisioned concurrency off permanently and rely on retries at the client side to mask cold starts.

Answer

Replace Lambda with a single always-on EC2 instance sized for peak demand to eliminate cold starts.

Question 2

A company stores user uploads in an S3 bucket. Objects are accessed rarely after upload, but when an object is accessed, it must be retrievable quickly (minutes to a few hours). Objects must be retained for at least 18 months. The team wants to reduce storage cost while meeting these requirements. Which lifecycle configuration best fits these requirements?

Accepted Answer

After 30 days, transition objects to S3 Glacier Instant Retrieval, and after 18 months, expire (delete) the objects.. Option B is correct because it transitions objects to S3 Glacier Instant Retrieval after 30 days, which provides millisecond retrieval for rarely accessed data, meeting the quick retrieval requirement. The 18-month expiration ensures compliance with the retention policy while minimizing storage costs compared to keeping data in S3 Standard.

Answer

Keep all objects in S3 Standard permanently to avoid lifecycle transition fees.

Answer

After 30 days, transition objects to S3 Intelligent-Tiering, and set expiration to 12 months.

Answer

After 30 days, transition objects to S3 Glacier Deep Archive, and set expiration to 18 months.

Question 3

A media processing pipeline runs batch jobs overnight. The jobs are stateless, can be restarted from checkpoints, and can tolerate interruptions. The team wants to minimize compute cost. Which EC2 approach is the best fit?

Accepted Answer

Use Spot Instances and design the jobs to handle interruptions by checkpointing and retrying.. Spot Instances offer significant cost savings (up to 90% off On-Demand) but can be reclaimed by AWS with a 2-minute interruption notice. Since the batch jobs are stateless, checkpointable, and interruption-tolerant, they are an ideal workload for Spot Instances. Designing the jobs to save progress to a durable checkpoint (e.g., Amazon S3) and automatically retry on interruption ensures resilience while minimizing compute cost.

Answer

Use On-Demand instances to guarantee uninterrupted capacity.

Answer

Use a 1-year Reserved Instance for the current instance type and lock the fleet to it.

Answer

Use Savings Plans but still treat interruptions as failures that require manual intervention.

Question 4

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?

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 5

An EC2 workload runs in one region on a single instance type. For the last month, CloudWatch metrics show average CPU utilization of 12% and no sustained memory pressure. The team wants to reduce cost while maintaining the current performance level. What is the best first step?

Accepted Answer

Use AWS Compute Optimizer to get recommendations for instance type and size changes.. AWS Compute Optimizer analyzes historical utilization metrics (CPU, memory, I/O) and provides actionable recommendations for right-sizing instances. Given the average CPU utilization of only 12% and no memory pressure, Compute Optimizer will likely recommend a smaller instance type or family that matches the workload's actual resource needs, reducing cost without affecting performance.

Answer

Increase the instance size to reduce the risk of performance regression.

Answer

Switch to Spot Instances immediately to reduce cost regardless of utilization.

Answer

Disable detailed monitoring to lower CloudWatch charges.

Question 6

A company hosts an application on EC2 instances in private subnets. The instances must (1) read objects from Amazon S3 and (2) retrieve secrets from AWS Secrets Manager. The team currently sends all outbound traffic through a NAT gateway to reach both services. They want to reduce monthly cost while keeping traffic private (no internet egress) and without changing application logic. Which change is the most cost-effective?

Accepted Answer

Create a Gateway VPC endpoint for S3 and an Interface VPC endpoint for Secrets Manager, and ensure the subnet route tables / endpoint routing directs those service calls to the endpoints instead of the NAT gateway.. Option A is correct because Gateway VPC Endpoints for S3 and Interface VPC Endpoints for Secrets Manager allow private connectivity to these AWS services without traversing the internet or a NAT gateway. This eliminates NAT gateway hourly charges and data processing fees, reducing costs while keeping traffic within the AWS network. The application logic remains unchanged as the endpoints are accessed via the same DNS names, with route tables directing traffic to the endpoints instead of the NAT gateway.

Answer

Keep the NAT gateway, but add AWS WAF rules to block non-service outbound requests to reduce NAT usage.

Answer

Disable IPv4 on the VPC subnets and rely on IPv6-only egress to reduce NAT gateway costs.

Answer

Replace the NAT gateway with a VPC firewall appliance instance to proxy outbound calls and reduce NAT fees.

Question 7

A media company runs a fleet of EC2 instances using Auto Scaling across multiple instance families (for example, m-series and c-series) in a single region. The business wants to commit to steady usage for one year to reduce cost, but the application team must retain flexibility to switch instance families and scale up/down as demand changes. They need the cost-reduction approach that best matches this flexibility. Which option is the best fit?

Accepted Answer

Purchase Compute Savings Plans so the commitment applies regardless of instance family changes within the selected scope.. Compute Savings Plans provide the most flexibility because they apply to any EC2 instance family (including m-series and c-series) within a region, automatically adjusting to instance family changes and scaling. This matches the requirement to commit to steady usage for one year while retaining the ability to switch families and scale up/down, offering up to 66% savings over On-Demand without locking the application to a specific instance type.

Answer

Purchase Standard Reserved Instances tied to a specific instance family and region, so the application can only run on the selected family.

Answer

Purchase Spot Instances for all capacity and disable On-Demand fallback to guarantee the lowest cost.

Answer

Rely only on On-Demand and reduce cost by using a CloudFront-only approach for all dynamic content.

Question 8

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 9

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.. Option A is correct because 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 10

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 11

A media company uploads raw video thumbnails to an S3 bucket every hour. The application needs these thumbnails for active browsing for the first 7 days. After day 7, access becomes rare. Requirements: - Objects must remain available in S3 for at least 180 days total. - After day 7, the team can tolerate retrieval latency in the range of minutes to hours. - They want to minimize storage cost while keeping the ability to read objects (no application changes required). Which storage strategy is the most cost-optimized fit?

Accepted Answer

Use a lifecycle rule to transition objects to S3 Glacier Flexible Retrieval after day 7 and expire them after day 180.. Option B is correct because S3 Glacier Flexible Retrieval provides retrieval times from minutes to hours, which matches the tolerance for rare access after day 7, and offers the lowest storage cost among the options for data that is rarely accessed. A lifecycle rule transitions objects from S3 Standard (used for the first 7 days of active browsing) to Glacier Flexible Retrieval on day 7, then expires them after day 180, meeting the 180-day retention requirement without application changes.

Answer

Use a bucket-level lifecycle rule to transition objects to S3 Standard-IA on day 7 and then expire them after day 180.

Answer

Keep all objects in S3 Standard for 180 days, and enable S3 Intelligent-Tiering only if the bucket’s access frequency is above a threshold.

Answer

Use a lifecycle rule to transition objects to S3 Glacier Instant Retrieval after day 7 and expire them after day 180.

Question 12

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.. Option A is correct because 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 13

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.. Option B is correct because 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 14

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 15

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.. Option A is correct because 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.