SAA-C03 Design Cost-Optimized Architectures Practice Test 18 — 15 Questions

Question 1

A SaaS provider runs a multi-tenant application on Amazon RDS for PostgreSQL. The database is 2 TB and experiences steady read-heavy traffic during business hours. The provider wants to offload read traffic to reduce load on the primary instance and lower cost compared to scaling up the primary. The application can tolerate slightly stale reads for reporting queries. Which solution is MOST cost-effective?

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

Accepted Answer

Create a read replica and route reporting queries to it.. A read replica offloads read-only reporting queries from the primary instance, reducing contention and allowing the primary to remain appropriately sized. Because asynchronous replication introduces slight lag, the application's tolerance for stale reads makes this acceptable. This approach is more cost-effective than scaling up the primary or enabling Multi-AZ, which does not provide readable standby capacity.

Answer

Enable Multi-AZ deployment and route reporting queries to the standby instance.

Answer

Migrate the database to Amazon DynamoDB with on-demand capacity mode.

Answer

Increase the size of the primary RDS instance to a larger instance class.

Question 2

A small e-commerce company hosts its website on a single EC2 instance in a public subnet. The site receives low but steady traffic. The company wants to reduce cost and is willing to accept a brief interruption if the instance is terminated. The workload can be restarted automatically. Which EC2 purchasing option should the company use to minimize cost?

Accepted Answer

Spot Instances. Spot Instances provide the deepest discounts and are designed for workloads that can tolerate interruptions. Since the company accepts a brief interruption and can restart automatically, Spot aligns perfectly with the workload characteristics. On-Demand, Reserved Instances, and Dedicated Hosts are either more expensive or require commitments that are unnecessary for this flexible, low-traffic website.

Answer

On-Demand Instances

Answer

Reserved Instances with a 3-year term and all upfront payment

Answer

Dedicated Hosts

Question 3

A company runs a media transcoding service on Amazon EC2 instances behind an Application Load Balancer. The workload is steady at 60% CPU utilization from 08:00 to 18:00 local time on weekdays and drops to under 5% overnight and on weekends. A solutions architect must reduce compute costs without changing the application code or degrading transcoding throughput during peak hours. (Choose two.)

Accepted Answer

Configure a scheduled scaling action on the Auto Scaling group to reduce desired capacity outside the 08:00-18:00 weekday window.. The workload has two distinct cost components: an always-on baseline and a predictable daily peak. A Compute Savings Plan discounts the continuous baseline usage across any instance family or Region, while scheduled scaling trims the fleet during the known low-traffic windows. Together they reduce spend without touching application code, preserving peak throughput, and avoiding the interruption risk that Spot would introduce.

Answer

Replace all On-Demand instances with Spot Instances in a single Availability Zone.

Answer

Move the transcoding workload to a larger instance type so fewer instances are needed at peak.

Answer

Enable detailed CloudWatch monitoring at one-minute resolution for every instance in the group.

Question 4

A company runs a REST API on AWS Lambda behind Amazon API Gateway. The API is used by internal clients during a two-hour batch window each night and is completely idle the rest of the day. The team is concerned about the cost of API Gateway and wants to minimize it without changing the API contract for clients. Which change should a solutions architect recommend?

Accepted Answer

Use an HTTP API instead of the REST API so requests are billed at the lower HTTP API rate.. The workload is bursty and idle most of the day, so a per-request pricing model is the right foundation and provisioned or always-on resources should be avoided. Moving from a REST API to an HTTP API lowers the per-request charge while keeping the same client-facing contract, so the nightly batch pays less and the idle hours cost nothing. Caching and provisioned concurrency would both add continuous charges.

Answer

Replace API Gateway and Lambda with an Application Load Balancer forwarding to an Auto Scaling group of EC2 instances.

Answer

Keep the REST API but enable API caching with a one-hour time-to-live.

Answer

Switch the API from a REST API to an HTTP API and configure the Lambda function with provisioned concurrency.

Question 5

A company runs an Amazon DynamoDB table that stores session data for a consumer application. The table is 800 GB and receives highly variable read and write traffic with sharp, unpredictable peaks during marketing campaigns. The team currently provisions 20,000 read capacity units and 10,000 write capacity units and frequently sees throttling during peaks and wasted capacity between them. A solutions architect must reduce cost and eliminate throttling with the least operational effort. Which solution meets these requirements?

Accepted Answer

Switch the table to on-demand capacity mode.. The traffic pattern is spiky and unpredictable, which is exactly where provisioned capacity with reactive auto scaling falls short and where on-demand mode excels. On-demand billing charges per request unit consumed, scales instantly to any traffic level, and removes the need to tune capacity, so it both eliminates throttling and avoids paying for idle provisioned throughput between campaigns.

Answer

Increase provisioned capacity to 60,000 read capacity units and 30,000 write capacity units and enable auto scaling.

Answer

Add a DynamoDB Accelerator (DAX) cluster in front of the table and keep the current provisioned capacity.

Answer

Enable DynamoDB auto scaling with a target utilization of 70% for both read and write capacity.

Question 6

A company hosts a public-facing static website and a set of downloadable software packages. Users are distributed globally, and the packages are large, so the company wants to reduce data transfer costs and improve download latency. The content changes only when a new release is published, a few times per month. Which solution should a solutions architect recommend?

Accepted Answer

Store the content in Amazon S3 and distribute it through an Amazon CloudFront distribution with a cache policy that sets a long time-to-live.. For globally distributed, cacheable static content, a CDN is the standard cost and latency optimization. CloudFront caches objects at edge locations, so most requests are served without touching the S3 origin, and the edge data transfer rate is lower than direct S3 internet transfer. A long time-to-live is appropriate because the content changes only a few times per month.

Answer

Replicate the S3 bucket to every AWS Region and return Region-specific URLs to users.

Answer

Move the content to Amazon EFS and mount the file system from EC2 instances in each Region.

Answer

Serve the website and packages from an Amazon S3 bucket in the primary Region and enable S3 Transfer Acceleration.

Question 7

A company runs a batch processing job on Amazon EC2 instances that takes approximately 4 hours to complete. The job can be interrupted and resumed from a checkpoint. The company wants to minimize the cost of running this job. Which pricing model should they use?

Accepted Answer

Spot Instances. Spot Instances are the most cost-effective choice for interruptible batch jobs that can checkpoint and resume. They leverage spare EC2 capacity at steep discounts, and the job's design tolerates interruptions. Reserved and On-Demand pricing do not offer the same savings for this use case, and Dedicated Hosts are overkill. Thus, Spot Instances align with both the workload characteristics and the cost objective.

Answer

Dedicated Hosts

Answer

Reserved Instances

Answer

On-Demand Instances

Question 8

A company stores 500 TB of archival data in Amazon S3. The data is accessed only once a year for compliance audits. The company wants the most cost-effective storage solution that still allows retrieval within 48 hours. Which S3 storage class should they use?

Accepted Answer

S3 Glacier Deep Archive. S3 Glacier Deep Archive is the most cost-effective storage class for long-term retention of data that is rarely accessed and can tolerate retrieval times of 12 hours or more. The 48-hour retrieval requirement is satisfied, and the annual access pattern aligns with its design. Other classes either cost more or do not offer the same savings for archival data.

Answer

S3 Intelligent-Tiering

Answer

S3 Standard

Answer

S3 One Zone-IA

Question 9

A financial analytics team runs a nightly Monte Carlo simulation on a cluster of Amazon EC2 instances. The simulation writes checkpoint files to an Amazon EBS volume, and the job can be safely restarted from the last checkpoint if interrupted. The team needs the lowest possible compute cost and can tolerate interruptions. The job must run every night and finish within a 6-hour window. Which solution meets these requirements MOST cost-effectively?

Accepted Answer

Use Spot Instances with a persistent request and checkpointing to EBS.. Spot Instances are the most cost-effective choice for fault-tolerant, interruptible workloads, offering steep discounts over On-Demand. Because the simulation can resume from checkpoints, Spot interruptions are acceptable. A persistent Spot request helps maintain capacity to complete the job within the nightly window, while checkpointing to EBS preserves progress. Other purchasing options either cost more or do not suit the interruptible pattern.

Answer

Use On-Demand EC2 instances with a placement group for low-latency networking.

Answer

Use Dedicated Hosts to ensure physical isolation for the simulation.

Answer

Purchase a 1-year Standard Reserved Instance for each instance in the cluster.

Question 10

A company runs a batch processing job on Amazon EC2 instances that runs for 4 hours every night. The job can be interrupted and restarted from a checkpoint. The company wants to minimize compute costs for this job. Which solution is MOST cost-effective?

Accepted Answer

Run the job on Spot Instances.. Spot Instances are the most cost-effective choice for interruptible, checkpointed batch workloads because they leverage spare EC2 capacity at a steep discount. The job runs for a short, predictable duration nightly and can resume after interruptions, which perfectly matches Spot's interruption model. Reserved Instances and Dedicated Hosts involve commitments or high fixed costs that are wasteful for intermittent usage, and On-Demand is more expensive than Spot.

Answer

Run the job on On-Demand Instances.

Answer

Use Dedicated Hosts for the instances.

Answer

Purchase a 1-year All Upfront Reserved Instance for the instances.

Question 11

A company runs a microservices application on Amazon ECS with AWS Fargate. The application experiences variable traffic throughout the day, with peak hours during business hours and minimal traffic at night. The company wants to optimize costs without affecting performance. Which action should they take?

Accepted Answer

Configure ECS Service Auto Scaling to adjust the number of tasks based on demand.. ECS Service Auto Scaling dynamically adjusts task count based on demand, ensuring the application scales with traffic while minimizing costs during idle periods. This is the most direct and effective cost optimization for variable workloads on Fargate. Other options either do not apply to Fargate or do not provide automatic elasticity, risking higher costs or performance issues.

Answer

Purchase Reserved Instances for Fargate tasks.

Answer

Migrate the application to Amazon EC2 instances with Spot Instances.

Answer

Use a larger Fargate task size to reduce the number of tasks.

Question 12

A company runs a containerized web application on Amazon ECS with a steady baseline of 10 tasks that must run continuously. During business hours, traffic spikes require up to 30 additional tasks that can be terminated at any time. The company wants to minimize costs while ensuring the baseline tasks are always available. Which combination of purchasing options should be used for the ECS tasks?

Accepted Answer

Use Reserved Instances or Savings Plans for the baseline and Spot Instances for the additional tasks.. The baseline of 10 tasks runs continuously, so Reserved Instances or Savings Plans offer the best discount for that predictable usage. The additional tasks are variable and can be interrupted, making Spot Instances ideal for cost savings. Combining these two purchasing options aligns cost with the characteristics of each workload component, ensuring availability for the baseline while minimizing spend on the spikes.

Answer

Use Dedicated Hosts for the baseline and On-Demand Instances for the additional tasks.

Answer

Use On-Demand Instances for the baseline and Spot Instances for the additional tasks.

Answer

Use Spot Instances for all tasks, including the baseline, to maximize savings.

Question 13

A company runs a real-time bidding platform on Amazon EC2 instances that must respond within milliseconds. The workload is highly variable, with unpredictable spikes during business hours. The company wants to minimize costs while ensuring the application always has enough capacity to handle sudden traffic surges. Which pricing model should they use?

Accepted Answer

Use On-Demand Instances with an Auto Scaling group.. For unpredictable, latency-sensitive workloads, On-Demand Instances combined with Auto Scaling provide the necessary elasticity and cost control. You pay only for what you use, and Auto Scaling ensures capacity matches demand. Reserved or Savings Plans are better for steady-state usage, while Spot Instances introduce interruption risk. Dedicated Hosts are cost-prohibitive and inflexible for this scenario.

Answer

Use a Savings Plan with a 3-year term to cover all compute usage.

Answer

Purchase a 1-year All Upfront Reserved Instance for the baseline capacity and use Spot Instances for spikes.

Answer

Use Dedicated Hosts to ensure performance and reduce costs.

Question 14

A company has a steady-state workload on Amazon EC2 that runs 24/7 for the next 3 years. They want to achieve the maximum possible discount and are willing to make a upfront payment. Which purchasing option should they choose?

Accepted Answer

Reserved Instances with All Upfront payment. Reserved Instances with All Upfront payment offer the maximum discount for a 3-year commitment on a steady-state workload. This option provides significant savings over On-Demand and is more reliable than Spot. Dedicated Hosts are not cost-optimized for general workloads. Therefore, All Upfront Reserved Instances are the best choice for maximum discount.

Answer

On-Demand Instances

Answer

Spot Instances

Answer

Dedicated Hosts with All Upfront payment

Question 15

A company stores 500 TB of archival data in Amazon S3. The data is accessed only for compliance audits, which occur once every two years. Retrieval times of up to 12 hours are acceptable. The company wants the lowest storage cost. Which S3 storage class should be used?

Accepted Answer

S3 Glacier Deep Archive. S3 Glacier Deep Archive is specifically designed for long-term retention of data that is rarely accessed, offering the lowest storage cost among S3 classes. It supports retrieval within 12 hours, which matches the acceptable retrieval time. For compliance data accessed every two years, it provides the most economical solution without unnecessary retrieval speed or monitoring overhead.

Answer

S3 One Zone-Infrequent Access (S3 One Zone-IA)

Answer

S3 Intelligent-Tiering

Answer

S3 Standard-Infrequent Access (S3 Standard-IA)