SAA-C03 Design Cost-Optimized Architectures Practice Test 10 — 15 Questions

Question 1

A media processing pipeline runs batch jobs on EC2. The jobs can tolerate interruptions because they checkpoint progress to durable storage and can restart. The total workload is variable week-to-week, and there is no need to guarantee capacity at specific times. To reduce compute cost while maintaining correctness, what EC2 purchase option and approach is the best fit?

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

Accepted Answer

Use EC2 Spot Instances with interruption handling and restart from checkpoints.. Spot Instances offer up to 90% cost savings compared to On-Demand and are ideal for fault-tolerant, stateless workloads that can checkpoint progress to durable storage. Since the batch jobs can tolerate interruptions and restart from checkpoints, Spot Instances provide the lowest compute cost while maintaining correctness. No other purchase option achieves the same level of cost reduction for this variable, interruption-tolerant workload.

Answer

Use All Upfront Reserved Instances sized for the average weekly workload to minimize cost.

Answer

Use On-Demand Instances and scale only during business hours to reduce idle time.

Answer

Use Savings Plans with a fixed hourly commitment to ensure capacity for the entire year.

Question 2

A development team expects their EC2 utilization to average about 40% of capacity across the next year. They want to lower costs but need flexibility to change instance families and sizes as requirements evolve (for example, moving from compute-optimized to memory-optimized instances). Which AWS purchasing commitment best meets the goal of reducing cost while keeping flexibility?

Accepted Answer

Compute Savings Plans, sized to the expected average usage, because they provide savings across instance families and usage types.. Compute Savings Plans offer the best balance of cost reduction and flexibility for this scenario. They provide up to 66% savings in exchange for a commitment to a consistent amount of compute usage (measured in $/hour), but unlike Reserved Instances, they automatically apply to any EC2 instance family, size, OS, or region (within a given AWS region). This allows the team to switch from compute-optimized to memory-optimized instances as needs evolve without losing the discount, directly meeting the requirement for flexibility while lowering costs.

Answer

All Upfront EC2 Instance Reserved Instances for a single instance family to maximize discount.

Answer

Spot Instances for the entire workload so they can avoid commitments entirely.

Answer

On-Demand Instances with increased Auto Scaling to match the peak month only.

Question 3

An S3 bucket stores user-uploaded images. Access patterns are unpredictable: some objects are never read again, while others are occasionally retrieved months later. The team wants to reduce storage cost without having to manually track access frequency or run periodic analyses. Which S3 storage and lifecycle approach is the best fit?

Accepted Answer

Enable S3 Intelligent-Tiering so objects can automatically move between access tiers based on observed access patterns.. S3 Intelligent-Tiering is the best fit because it automatically moves objects between access tiers (frequent, infrequent, archive instant, archive) based on changing access patterns, eliminating the need for manual tracking or lifecycle rules. This optimizes storage costs for unpredictable access patterns without requiring you to define fixed time-based transitions or perform periodic analyses.

Answer

Use S3 Glacier Instant Retrieval for all objects immediately to minimize storage cost.

Answer

Create a lifecycle rule that transitions objects to Standard-IA after a fixed 30 days, regardless of access.

Answer

Keep all objects in S3 Standard and reduce costs by enabling server access logging compression.

Question 4

A service runs in private subnets. It must call AWS APIs (for example, S3 and Secrets Manager). The team currently sends all outbound traffic through a NAT Gateway, and NAT charges have become a major cost driver. The workload must not traverse the public internet. What change most directly reduces NAT Gateway cost while maintaining private connectivity to those AWS services?

Accepted Answer

Replace the NAT Gateway route with VPC endpoints: use a Gateway VPC endpoint for S3 and an Interface VPC endpoint for Secrets Manager.. VPC endpoints allow private connectivity to AWS services without traversing the internet or a NAT Gateway. A Gateway VPC endpoint for S3 uses route table entries to reach S3 privately, and an Interface VPC endpoint for Secrets Manager uses an elastic network interface with a private IP. This eliminates NAT Gateway data processing charges entirely while keeping traffic within the AWS network.

Answer

Continue using the NAT Gateway but reduce CloudWatch log retention to 1 day.

Answer

Launch a bastion host in a public subnet and force private instances to use SSH tunneling for API calls.

Answer

Switch to public subnets and attach security groups with the same rules to limit inbound access.

Question 5

A static web application uses CloudFront with an S3 origin for assets (JavaScript, CSS, images). After deploying a new frontend build, the CloudFront cache hit ratio dropped significantly because the S3 origin receives many repeated requests for the same assets. The team notices that requests now include the Authorization header in asset requests. Which change is most likely to restore cache efficiency and reduce origin request costs?

Accepted Answer

Update the CloudFront cache policy so that Authorization is excluded from the cache key for static asset paths.. The drop in cache hit ratio is caused by the Authorization header being included in asset requests, which makes each request unique from CloudFront's perspective, preventing cache reuse. By updating the CloudFront cache policy to exclude the Authorization header from the cache key for static asset paths, CloudFront can treat identical asset requests as cache hits, restoring cache efficiency and reducing origin load.

Answer

Keep the Authorization header but increase the cache TTL to 1 year to reduce revalidation frequency.

Answer

Remove CloudFront and serve assets directly from the S3 website endpoint to reduce CloudFront charges.

Answer

Switch the S3 origin from private access to public access so CloudFront can cache assets more effectively.

Question 6

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.. 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 7

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.. 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 8

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 9

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 10

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 11

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.. 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 12

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 13

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 14

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 15

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.. 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.