SOA-C02 Cost and Performance Optimization Practice Test 3 — 15 Questions

Question 1

A company runs a web application on EC2 instances in an Auto Scaling group behind an ALB. The application experiences variable traffic, with peak usage during business hours and low traffic at night. The SysOps administrator wants to reduce costs while maintaining performance. The current setup uses On-Demand instances only. The application is stateful and stores session data in an ElastiCache Redis cluster. The administrator has identified that the application can handle Spot Instance interruptions gracefully by redirecting users to a fallback page. The company has a budget of $10,000 per month for EC2 instances, and current costs are $8,000 per month. The administrator wants to reduce costs further without compromising availability for most users. Which solution is MOST cost-effective?

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

Accepted Answer

Use a mixed instances policy with Spot Instances during off-peak hours and On-Demand during peak hours, using Auto Scaling scheduled scaling.. The most cost-effective because it leverages Spot Instances during off-peak hours (low traffic) to reduce costs significantly while maintaining On-Demand instances during peak hours to ensure performance and availability. Auto Scaling scheduled scaling aligns with the predictable traffic pattern. Option A is less cost-effective because a large On-Demand base capacity would increase costs unnecessarily; Spot can be used more aggressively during off-peak. Option B is not ideal because Reserved Instances require upfront commitment and are best for steady-state workloads, not variable traffic. Option C would risk excessive Spot interruptions during peak hours, degrading user experience despite the fallback page.

Answer

Increase the On-Demand base capacity to handle peak load and use Spot for any additional capacity.

Answer

Purchase Reserved Instances for the minimum expected capacity and use On-Demand for the rest.

Answer

Use only Spot Instances at all times to maximize savings, and rely on the fallback page for interruptions.

Question 2

A company runs a data processing pipeline on AWS. The pipeline consists of EC2 instances that process data from an S3 bucket and write results to another S3 bucket. The processing job runs every hour and takes approximately 45 minutes. The current setup uses On-Demand instances. The SysOps administrator wants to reduce costs because the monthly EC2 bill is $5,000. The application is fault-tolerant and can handle interruptions by reprocessing data from the last checkpoint. The administrator has tested Spot Instances and found that they are interrupted about 10% of the time. The company has a strict requirement that the job must complete within 60 minutes every hour. Which solution would reduce costs while ensuring the job completes on time?

Accepted Answer

Use a Spot Fleet with a fallback to On-Demand if Spot capacity is not available.. A Spot Fleet with a fallback to On-Demand ensures the job completes within the 60-minute window even if Spot Instances are interrupted, while reducing costs by using cheaper Spot Instances when available. Option A is wrong because Reserved Instances require a 1- or 3-year commitment and may not be cost-effective for a job that runs only 45 minutes per hour, leading to wasted capacity. Option B is wrong because using a single larger On-Demand instance would increase costs, not reduce them. Option D is wrong because using Spot Instances only, even with more instances, risks exceeding the 60-minute deadline due to the 10% interruption rate; the fallback to On-Demand is necessary to guarantee completion time.

Answer

Purchase Reserved Instances for the expected capacity to get a discount.

Answer

Use a single larger On-Demand instance to complete the job faster.

Answer

Use Spot Instances only and increase the number of instances to compensate for interruptions.

Question 3

An application running on Amazon EC2 generates a large number of small files that are stored temporarily and deleted after 24 hours. The files are accessed frequently within the first hour and then rarely. Which Amazon S3 storage class is MOST cost-effective for this use case?

Accepted Answer

S3 Intelligent-Tiering. S3 Intelligent-Tiering (Option B). This storage class automatically moves objects between a frequent access tier and an infrequent access tier based on changing access patterns, making it cost-effective for unpredictable or shifting access patterns. In this use case, files are accessed frequently in the first hour and then rarely, so Intelligent-Tiering will initially store them in the frequent access tier and then move them to the infrequent access tier after 30 days of no access, reducing costs. Option A (S3 Glacier Deep Archive) is unsuitable due to a 180-day minimum storage charge and retrieval times of hours, which does not match the 24-hour retention. Option C (S3 One Zone-Infrequent Access) is not ideal because it has a 30-day minimum storage charge and is designed for data accessed infrequently but with quick retrieval, not for a pattern that starts with frequent access. Option D (S3 Standard) would be unnecessarily expensive for the data after the first hour when it is rarely accessed.

Answer

S3 Glacier Deep Archive

Answer

S3 One Zone-Infrequent Access

Answer

S3 Standard

Question 4

A company runs a stateless web application on EC2 instances in an Auto Scaling group. The application is deployed across multiple Availability Zones. During a recent traffic spike, the Auto Scaling group launched more instances than expected, increasing costs. The SysOps administrator needs to prevent unexpected scaling while maintaining availability. What should the administrator do?

Accepted Answer

Configure scaling cooldowns to limit launch rate.. Scaling cooldowns add a waiting period after a scaling activity before another can begin, which prevents the Auto Scaling group from launching instances in rapid succession during a spike. This directly addresses the 'more instances than expected' problem while preserving multi-AZ availability.

Answer

Use a simple scaling policy instead of a dynamic scaling policy.

Answer

Set a lower maximum instance count in the Auto Scaling group.

Answer

Reduce the number of Availability Zones to one.

Question 5

A company is using Amazon EBS volumes for a high-performance database. The volumes are gp2 type. The database workload is write-intensive, and the company is experiencing high costs due to provisioned IOPS. The database team wants to maintain performance while reducing costs. Which EBS volume type should the company use?

Accepted Answer

gp3. gp3 volumes are the correct choice because they provide a baseline performance that is independent of volume size, and customers only pay for provisioned IOPS above the baseline. This makes them cost-effective for write-intensive database workloads. Option A (sc1) is wrong because Cold HDD volumes are designed for infrequently accessed data and offer low IOPS, making them unsuitable for high-performance databases. Option B (st1) is wrong because Throughput Optimized HDD volumes are optimized for large, sequential workloads, not random I/O typical of databases. Option C (io2 Block Express) is wrong because while it offers high performance, it is more expensive than gp3 for workloads that do not require the extreme performance of io2.

Answer

sc1 (Cold HDD)

Answer

st1 (Throughput Optimized HDD)

Answer

io2 Block Express

Question 6

A company runs a production workload on Amazon EC2 instances. The SysOps administrator wants to implement a cost optimization strategy that does not compromise availability. Which TWO actions should the administrator take?

Accepted Answer

Use Spot Instances for fault-tolerant and stateless workloads.. Option A is correct because Spot Instances can reduce compute costs by up to 90% compared to On-Demand, and using them for fault-tolerant, stateless workloads preserves availability since interruptions can be absorbed without impacting the production service. Option C is correct because Reserved Instances (Standard or Convertible, 1- or 3-year terms) provide significant discounts for steady-state baseline capacity that is always running, without reducing availability. Option B is not appropriate as a primary cost-optimization action here because terminating idle instances requires careful identification and could risk removing capacity needed for availability if misapplied. Option D is incorrect because downsizing all workloads can degrade performance and availability, and not every workload can run on smaller instance types. Option E is incorrect because consolidating into a single Availability Zone reduces resilience and violates the requirement not to compromise availability.

Answer

Identify and terminate idle instances.

Answer

Use smaller instance types for all workloads.

Answer

Use a single Availability Zone to reduce data transfer costs.

Question 7

A company is using Amazon S3 to store log files. The logs are accessed frequently for the first 30 days and then rarely, but must be retained for 7 years for compliance. Which TWO actions would optimize storage costs while maintaining accessibility?

Accepted Answer

Transition objects to S3 Glacier Deep Archive after 365 days.. Option C is correct because an S3 lifecycle policy that transitions objects to S3 Standard-IA after 30 days matches the access pattern: logs are frequently accessed for the first 30 days (kept in S3 Standard) and then rarely accessed, and Standard-IA offers lower storage cost for infrequently accessed data while keeping objects immediately retrievable. Option B is correct because transitioning to S3 Glacier Deep Archive after 365 days moves long-term compliance data to the lowest-cost S3 storage class, which is appropriate for data retained up to 7 years and rarely accessed, while still maintaining accessibility (retrieval within hours). Option A is wrong because deleting objects older than 90 days violates the 7-year compliance retention requirement. Option D is wrong because transitioning directly to S3 Glacier after 30 days skips the cheaper Standard-IA tier for the rarely-accessed-but-still-occasionally-needed period and is less cost-optimal than the Standard-IA-then-Deep-Archive approach. Option E is wrong because S3 Intelligent-Tiering is designed for unknown or changing access patterns and does not include the Glacier Deep Archive tier, so it would not achieve the lowest-cost long-term compliance retention.

Answer

Delete objects older than 90 days.

Answer

Transition objects directly to S3 Glacier after 30 days.

Answer

Use S3 Intelligent-Tiering to automatically move objects.

Question 8

A SysOps administrator needs to reduce costs for an Amazon RDS for PostgreSQL database. The database is used for a reporting application that only runs during business hours (9 AM to 5 PM). Which TWO actions would reduce costs without losing data?

Accepted Answer

Take a snapshot before stopping to preserve data.. Stopping the database during off-hours (Option E) stops billing for compute hours while preserving the data. Taking a snapshot before stopping (Option A) ensures data is preserved, but it is not required to save costs—stopping alone saves costs. However, the question requires preserving data, so combining stopping with a snapshot is the safest approach. Option B (deleting and restoring) risks data loss and is inefficient. Option C (converting to a read replica) does not directly reduce costs. Option D (Multi-AZ) increases costs.

Answer

Delete the database during off-hours and restore it each morning.

Answer

Convert the database to a read replica of another database.

Answer

Use a Multi-AZ cluster for high availability.

Question 9

A SysOps administrator notices that an S3 bucket's storage costs have increased significantly. The bucket stores log files and is configured with S3 Standard storage class. Most logs are accessed only once after 30 days. Which action will reduce costs without affecting data retrieval?

Accepted Answer

Create a lifecycle policy to transition objects to S3 Glacier Instant Retrieval after 30 days.. S3 Glacier Instant Retrieval is designed for long-lived, rarely accessed data that still requires immediate (millisecond) retrieval when needed. It offers storage costs up to 68% lower than S3 Standard-IA while maintaining the same low-latency access, making it ideal for log files accessed only once after 30 days. Since the requirement is to reduce costs without affecting data retrieval, this class perfectly matches the access pattern and retrieval performance needs.

Answer

Create a lifecycle policy to transition objects to S3 Standard-IA after 30 days.

Answer

Create a lifecycle policy to transition objects to S3 Glacier Deep Archive after 30 days.

Answer

Create a lifecycle policy to transition objects to S3 One Zone-IA after 30 days.

Question 10

A company has a production environment with multiple EC2 instances. They want to ensure that all instances are covered by a Reserved Instance (RI) to maximize cost savings. Which AWS service can automatically apply unused RIs to new instances?

Accepted Answer

AWS Cost Explorer. None of the listed services automatically apply unused Reserved Instances (RIs) to new instances. The application of unused RIs is handled automatically by AWS billing. AWS Cost Explorer provides RI utilization reports and recommendations, but does not apply RIs. AWS Systems Manager manages operational tasks, AWS Trusted Advisor offers best practice checks, and AWS Config evaluates resource configurations. None of these services perform automatic RI application.

Answer

AWS Systems Manager

Answer

AWS Trusted Advisor

Answer

AWS Config

Question 11

A company is using a t3.medium EC2 instance for a development web server. The instance is underutilized most of the time. Which TWO actions would optimize costs? (Choose TWO.)

Accepted Answer

Downsize the instance to t3.small.. Option B is correct because the t3.medium instance is underutilized, so downsizing to t3.small reduces the hourly compute cost while still meeting the development web server's low demand. Option C is correct because purchasing a Reserved Instance for the instance provides a significant discount (up to 72% versus On-Demand) in exchange for a 1- or 3-year commitment, which is appropriate for a steady, predictable development workload. Option A is incorrect because EBS optimization is a performance feature and does not reduce EC2 compute costs. Option D is incorrect because On-Demand is the default, most expensive pricing model and does not optimize costs. Option E is incorrect because Spot Instances can be interrupted with a two-minute warning, making them unsuitable for a development web server that needs to remain available.

Answer

Enable EBS optimization.

Answer

Change the instance to On-Demand.

Answer

Use Spot Instances for the workload.

Question 12

A company is using AWS Direct Connect to connect its on-premises data center to AWS. The company notices that data transfer costs are increasing. The company wants to reduce data transfer costs without impacting performance. Which action should the company take?

Accepted Answer

Use Direct Connect gateway to connect to multiple VPCs across regions.. A Direct Connect gateway allows you to connect to multiple VPCs in different AWS Regions using a single Direct Connect connection. This consolidation reduces the number of separate connections and virtual interfaces, thereby lowering overall data transfer costs because you avoid paying for multiple connections' data transfer charges. In contrast, VPC endpoints reduce data transfer costs only for traffic to S3 and DynamoDB, not for general data transfer. Increasing bandwidth or adding VPN encryption does not reduce costs.

Answer

Increase the bandwidth of the Direct Connect connection to improve performance.

Answer

Set up a VPN connection over the Direct Connect to encrypt traffic.

Answer

Use VPC endpoints for S3 and DynamoDB to reduce data transfer costs.

Question 13

A company runs a production database on an Amazon RDS for PostgreSQL instance. The company notices that the database is experiencing high CPU utilization during peak hours, causing performance degradation. The company wants to improve performance while minimizing cost. Which solution should the company implement?

Accepted Answer

Add an Amazon RDS read replica to offload read traffic.. Adding an Amazon RDS read replica offloads read traffic from the primary database, reducing CPU utilization on the primary instance. This is a cost-effective way to improve performance for read-heavy workloads, as read replicas can serve read queries while the primary handles writes. It also provides additional read capacity without scaling up the primary instance, which can be more expensive.

Answer

Create a Multi-AZ deployment for high availability.

Answer

Implement Amazon ElastiCache in front of the database.

Answer

Scale up the DB instance class to a larger size.

Question 14

A company has a stateful web application that requires session persistence. The application is deployed on EC2 instances behind an Application Load Balancer. The company wants to improve performance by caching frequently accessed data. Which solution is MOST cost-effective?

Accepted Answer

Use Amazon ElastiCache with Memcached to cache session data and frequently accessed data.. Amazon ElastiCache with Memcached provides an in-memory cache that can store session data and frequently accessed data, reducing database load and improving performance. It is cost-effective because Memcached is a simple, high-performance caching layer that scales horizontally and integrates with EC2 instances. This directly addresses the need for caching while maintaining session persistence.

Answer

Increase the instance size of the EC2 instances to improve performance.

Answer

Use Amazon CloudFront to cache static and dynamic content at the edge.

Answer

Enable sticky sessions (Session Affinity) on the ALB.

Question 15

A company runs a critical application on an Amazon RDS for MySQL DB instance. The company needs to ensure high availability and automatic failover in the event of a failure. The company also wants to optimize costs. Which solution should the company implement?

Accepted Answer

Create a Multi-AZ deployment for the RDS instance.. A Multi-AZ deployment for the RDS instance (B) provides high availability and automatic failover by maintaining a synchronous standby replica in a different Availability Zone. It automatically fails over to the standby in case of failure, ensuring minimal downtime. This solution also optimizes costs compared to other options because it only requires one standby instance and no manual intervention.

Answer

Create a read replica in a different Availability Zone and manually promote it during failure.

Answer

Use Amazon RDS Proxy to manage connections and improve failover.

Answer

Use a larger DB instance class to improve performance and reliability.