SOA-C02 Cost and Performance Optimization Practice Test 4 — 15 Questions

Question 1

An administrator runs the above command to list EC2 instances. The company wants to optimize costs. Which instance should the administrator consider terminating first?

Accepted Answer

i-0mnop3456 (t3.medium, stopped in us-east-1c). A stopped instance (i-0mnop3456) incurs no compute charges but may still incur EBS storage costs, and it provides no running capacity — so it is the least useful and should be evaluated first for termination to eliminate residual storage charges. Among the options, terminating a stopped instance removes any lingering EBS volumes and snapshots associated with it, yielding immediate cost savings without impacting running workloads.

Answer

i-0efgh5678 (t3.large, running in us-east-1b)

Answer

i-0abcd1234 (t3.medium, running in us-east-1a)

Answer

i-0ijkl9012 (t3.xlarge, running in us-east-1a)

Question 2

An administrator attaches the above IAM policy to a user. The user needs to stop an EC2 instance to save costs. The user reports that they are unable to stop the instance. What is the MOST likely cause?

Accepted Answer

The instance is part of an Auto Scaling group.. The most likely cause is that the instance is part of an Auto Scaling group (ASG). Although the IAM policy allows ec2:StopInstances, stopping an instance that belongs to an ASG will not effectively reduce costs because the ASG will automatically launch a replacement instance to maintain the desired capacity. Additionally, ASG settings such as health checks or scale-in protection may prevent the instance from being stopped directly or cause it to be immediately replaced, making the stop action ineffective for cost savings. Therefore, the user's inability to stop the instance to save costs is due to the instance being managed by an Auto Scaling group.

Answer

The instance has termination protection enabled.

Answer

The IAM policy does not allow ec2:StopInstances.

Answer

The user does not have permission to describe instances.

Question 3

A company is running a production web application on EC2 instances. Which TWO actions would improve both cost efficiency and performance?

Accepted Answer

Purchase Reserved Instances for the baseline capacity.. Options B and E are correct. Purchasing Reserved Instances for the baseline capacity reduces cost compared to On-Demand pricing. Implementing Auto Scaling adjusts capacity based on demand, ensuring performance during peaks and cost savings during low traffic. Option A (detailed monitoring) incurs additional cost without direct performance benefit. Option C (terminating idle instances) saves cost but does not improve performance. Option D (larger instance types) may improve performance but typically increases cost, making it not cost-efficient.

Answer

Enable detailed monitoring on all instances.

Answer

Terminate all idle instances.

Answer

Use larger instance types for all instances.

Question 4

A company runs a production web application on Amazon EC2 instances behind an Application Load Balancer. The application experiences unpredictable traffic spikes. The operations team wants to optimize costs while maintaining performance during spikes. Which solution is MOST cost-effective?

Accepted Answer

Use Compute Savings Plans for the baseline and run the spikes on On-Demand instances.. Compute Savings Plans provide discounted pricing (up to 66% off On-Demand) in exchange for a 1- or 3-year commitment to a consistent hourly spend, and they automatically apply across EC2, Fargate, and Lambda regardless of instance family, region, or tenancy. This makes them ideal for covering the predictable baseline, while unpredictable spikes are absorbed by On-Demand instances that can be launched and terminated freely without commitment risk. This combination optimizes cost without sacrificing the elasticity needed during traffic surges.

Answer

Use Spot Instances to handle the spikes.

Answer

Purchase Reserved Instances for the expected baseline capacity.

Answer

Use Dedicated Hosts for the entire workload.

Question 5

A SysOps administrator is reviewing cost reports and notices that costs for Amazon S3 have increased significantly. The bucket stores log files that are accessed once a month for auditing. The logs are written daily, and each object is about 10 MB. The company needs to keep logs for 7 years. Which action will optimize costs while meeting retention requirements?

Accepted Answer

Use an S3 Lifecycle policy to transition objects to S3 Glacier Deep Archive after 30 days and expire after 7 years.. S3 Glacier Deep Archive is the lowest-cost storage class (about $0.00099/GB-month) and is designed for data accessed less than once per year with a 12-hour retrieval time — perfect for logs accessed only annually for audits. A lifecycle policy transitioning objects after 30 days and expiring them after 7 years meets both the cost and retention requirements.

Answer

Store the logs in an Amazon EBS volume.

Answer

Transition the logs to S3 Glacier Flexible Retrieval after 30 days.

Answer

Store the logs in S3 Standard and delete after 7 years.

Question 6

A company has a data processing job that runs on Amazon EMR. The job takes 2 hours to complete and runs once per day. The SysOps administrator wants to reduce costs without affecting the completion time. Which strategy is MOST effective?

Accepted Answer

Use Spot Instances for the task nodes in the EMR cluster.. Spot Instances are the most effective cost-reduction strategy for EMR task nodes because task nodes perform only transient processing and do not store HDFS data, so interruption risk is acceptable. Since the job runs for 2 hours and Spot capacity is typically available, using Spot for task nodes can reduce compute costs by up to 90% without affecting completion time, as the cluster can still finish within the same window.

Answer

Use a smaller number of larger EC2 instances.

Answer

Reduce the number of core nodes.

Answer

Purchase Compute Savings Plans for the EMR cluster.

Question 7

A SysOps administrator is managing a fleet of Amazon EC2 instances that run a batch processing job. The job runs for 30 minutes every hour. The administrator wants to optimize costs by using Spot Instances but must ensure that the job completes even if Spot Instances are interrupted. Which configuration should the administrator use?

Accepted Answer

Use a mixed instances policy with both On-Demand and Spot Instances, and configure the Spot allocation strategy to 'lowestPrice'.. A mixed instances policy with both On-Demand and Spot Instances ensures the batch job has a baseline of On-Demand capacity that survives Spot interruptions, while Spot Instances provide cost savings. The 'lowestPrice' allocation strategy selects the cheapest Spot pools, and the mixed policy's On-Demand base capacity guarantees the job completes even if Spot capacity is reclaimed. This balances cost optimization with completion reliability.

Answer

Launch Spot Instances in an Auto Scaling group with a capacity-optimized allocation strategy.

Answer

Use a Spot Fleet with a 'persistent' request type.

Answer

Use only On-Demand Instances to avoid interruptions.

Question 8

A SysOps administrator is optimizing costs for an Amazon RDS for PostgreSQL instance. The database is used for a reporting application that runs only during business hours (9 AM to 5 PM). Which TWO actions should the administrator take to reduce costs? (Choose TWO.)

Accepted Answer

Stop the database instance during non-business hours.. Option A is correct because stopping an RDS for PostgreSQL instance during non-business hours eliminates charges for the DB instance's compute hours while it is stopped (storage charges still apply), which directly reduces cost for a database that is only needed 9 AM to 5 PM. Option E is correct because converting a Multi-AZ deployment to Single-AZ removes the standby replica and its associated compute and storage costs, and since this is a reporting application that does not require high availability failover, Single-AZ is a cost-effective fit. Option B is incorrect because moving to a larger instance type increases, not decreases, the hourly compute cost. Option C is incorrect because increasing provisioned IOPS raises the storage/IOPS charges rather than lowering them. Option D is incorrect because purchasing a Reserved Instance is a commitment-based discount that only pays off for continuously running workloads, and it would not be cost-optimal for an instance that is stopped outside business hours.

Answer

Move to a larger instance type to handle peaks.

Answer

Increase the provisioned IOPS for better performance.

Answer

Purchase a Reserved Instance for the database instance.

Question 9

A company runs a web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The ALB is configured with a target group that has health checks. The application is experiencing intermittent 503 errors. The SysOps administrator needs to identify the root cause. Which THREE steps should the administrator take to diagnose the issue? (Choose THREE.)

Accepted Answer

Monitor the CloudWatch metric 'HealthyHostCount' for the target group.. Correct options: B, D, E. Option B is correct because monitoring the CloudWatch metric 'HealthyHostCount' for the target group helps determine if the number of healthy instances drops, which can cause 503 errors. Option D is correct because enabling and reviewing ALB access logs can reveal the client IPs and response codes to diagnose the intermittent 503 errors. Option E is correct because checking the target group health check logs helps identify if instances are failing health checks, leading to no healthy targets. Option A is wrong because security group rules for the ALB control allowed traffic but do not directly cause 503 errors; 503 errors typically indicate no healthy targets. Option C is wrong because increasing the unhealthy threshold makes the ALB less sensitive to failures but does not diagnose the root cause.

Answer

Check the security group rules for the ALB.

Answer

Increase the unhealthy threshold count in the health check settings.

Question 10

A SysOps administrator wants to reduce the cost of storing infrequently accessed data in Amazon S3. The data must be retained for 10 years for compliance. Which TWO actions should the administrator take? (Choose TWO.)

Accepted Answer

Use S3 Glacier Deep Archive as the destination for the lifecycle transition.. Correct options: A and D. Option A is correct because S3 Glacier Deep Archive is the cheapest storage class for long-term archival, ideal for 10-year compliance retention. Option D is correct because configuring an S3 Lifecycle policy to transition objects to S3 Glacier Deep Archive after 30 days reduces costs for infrequently accessed data. Option B is wrong because S3 Standard is expensive for infrequently accessed data and not suitable for long-term archiving. Option C is wrong because enabling S3 Versioning increases storage costs due to multiple versions and does not directly reduce costs. Option E is wrong because S3 Intelligent-Tiering has monitoring costs and is best for unknown access patterns; it does not automatically transition to Glacier Deep Archive.

Answer

Store the data in S3 Standard.

Answer

Enable S3 Versioning to protect against accidental deletion.

Answer

Use S3 Intelligent-Tiering to automatically optimize costs.

Question 11

A company runs a data analytics platform on AWS that processes large datasets using Amazon EMR. The EMR cluster consists of 1 master node (m5.xlarge) and 10 core nodes (r5.2xlarge). The cluster runs batch jobs that last 4 hours each, and the cluster is terminated after each job. The SysOps administrator notices that the cluster takes 15 minutes to provision and bootstrap before each job, which increases the total runtime and cost. The administrator wants to reduce the time and cost associated with cluster provisioning. The data is stored in Amazon S3, and the job scripts are stored in an S3 bucket. The administrator has considered using long-running clusters but is concerned about cost. Which approach should the administrator take to optimize both time and cost?

Accepted Answer

Use EMR Managed Scaling and keep the cluster running between jobs.. EMR Managed Scaling automatically adjusts the cluster size based on workload, and keeping the cluster running between jobs eliminates the 15-minute provisioning and bootstrap overhead for each job. Since the cluster is already running, subsequent jobs start immediately, reducing total runtime and cost. Managed Scaling ensures the cluster scales down to minimal capacity when idle, minimizing the cost of keeping it alive between jobs. This approach balances the need for faster job start times with cost efficiency, as opposed to terminating and recreating the cluster each time.

Answer

Switch the core nodes to Spot Instances to reduce costs.

Answer

Use a larger master node instance type to speed up bootstrapping.

Answer

Use Amazon FSx for Lustre as the data store to reduce I/O time.

Question 12

A company runs a critical web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The application is deployed in a single AWS region. The company wants to improve performance for users in other regions and reduce the load on the origin servers. The SysOps administrator decides to use Amazon CloudFront. After implementing CloudFront, the administrator notices that the cache hit ratio is very low (around 10%) for the dynamic API responses that are served by the application. These API responses are personalized per user and change frequently. The administrator wants to improve performance for these dynamic requests while still using CloudFront. The application uses cookies for session management and the API responses depend on the user's session. The administrator must ensure that users receive the correct personalized content. Which configuration should the administrator use?

Accepted Answer

Use Lambda@Edge to generate personalized responses at the edge without forwarding all requests to the origin.. The API responses are personalized per user and depend on session cookies, so caching them at the edge is ineffective. Using Lambda@Edge allows the administrator to run code at edge locations to generate personalized responses or modify requests/responses without forwarding all requests to the origin. This improves performance for dynamic content while ensuring users receive correct personalized content.

Answer

Configure CloudFront to use origin shield and enable keep-alive connections to the origin.

Answer

Configure CloudFront to forward cookies to the origin and enable caching based on cookies.

Answer

Disable caching for the API behavior in CloudFront and enable real-time logs.

Question 13

A company wants to reduce costs for a production Amazon RDS for MySQL DB instance that is running 24/7 but only heavily used during business hours (9 AM to 5 PM). Which TWO actions would be MOST effective in optimizing costs without significantly impacting performance during peak hours?

Accepted Answer

Purchase Reserved Instances for the DB instance.. Option B is correct because purchasing Reserved Instances for a steady-state, 24/7 RDS for MySQL instance yields significant savings (up to ~69% for 3-year All Upfront, or ~40% for 1-year No Upfront) compared to On-Demand pricing, and the instance runs continuously so the commitment is fully utilized. Option D is correct because RDS supports scheduling instance modifications via Application Auto Scaling (or EventBridge + Lambda) to scale the DB instance class down outside 9 AM–5 PM, cutting compute costs during the ~16 off-peak hours while restoring the larger class before peak usage. Option A is incorrect because Multi-AZ is a high-availability feature that roughly doubles cost and does not reduce spend. Option C is incorrect because gp3 is not a supported storage type for RDS for MySQL (RDS offers gp2, io1, and io2), and storage is not the dominant cost driver here. Option E is incorrect because RDS DB instances do not support Auto Scaling of instance class in the way EC2 Auto Scaling groups do; scaling must be scheduled or driven by Application Auto Scaling, not native Auto Scaling.

Answer

Enable Multi-AZ deployment for high availability.

Answer

Migrate from Provisioned IOPS (io1) storage to General Purpose (gp3) storage.

Answer

Enable Auto Scaling for the DB instance.

Question 14

A SysOps team manages a fleet of EC2 instances used for batch processing. The workload runs daily, taking approximately 6 hours. The instances are launched via an Auto Scaling group using On-Demand instances from a custom AMI. The team has noticed that while the instances are running, the CPU utilization is moderate, but the memory usage is high. After the batch completes, the instances are terminated. The team wants to reduce costs without changing the architecture. Which solution would be MOST cost-effective?

Accepted Answer

Modify the Auto Scaling group to use a mixed instances policy with a percentage of Spot Instances and a fallback to On-Demand.. The workload is a daily 6-hour batch job on an Auto Scaling group that terminates instances after completion, so there is no steady-state or predictable long-running usage to justify Reserved Instances or Savings Plans. A mixed instances policy with Spot Instances and On-Demand fallback can cut costs by up to 90% on the Spot portion while maintaining availability if Spot capacity is reclaimed. This directly reduces cost without changing the architecture.

Answer

Use a Compute Savings Plan covering the entire compute usage across the account.

Answer

Change the instance type to a memory-optimized family to reduce the number of instances needed.

Answer

Purchase Reserved Instances for the expected daily usage to get a lower hourly rate.

Question 15

A SysOps administrator manages a fleet of 40 Amazon EC2 instances that run a memory-intensive in-memory caching layer. Each instance uses 120 GiB of RAM and 8 vCPUs. The workload runs continuously and is expected to remain stable for the next 3 years. The administrator wants to minimize compute costs while keeping the same performance characteristics. Which action should the administrator take?

Accepted Answer

Purchase a 3-year Compute Savings Plan with a commitment equal to the steady-state compute usage.. The workload is steady, long-running, and memory-intensive, so a commitment-based discount is appropriate. A Compute Savings Plan provides up to 66% savings and automatically applies to any EC2 instance family, size, tenancy, or Region, as well as Fargate and Lambda. This preserves the ability to change instance types if the caching layer evolves, while still minimizing compute costs for the three-year horizon. Reserved Instances would lock the administrator into a specific configuration and offer less flexibility.

Answer

Purchase a 3-year No Upfront Convertible Reserved Instance for each instance.

Answer

Use Spot Instances with a capacity-optimized allocation strategy and a persistent request.

Answer

Purchase a 3-year All Upfront Reserved Instance for each instance, matching the instance family, size, and tenancy.