Cost optimization pillar in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Cost Optimization Principles

Which of the following best describes the primary goal of the Cost Optimization pillar in cloud architecture?

A Minimize cost while maintaining performance and reliability

B Maximize resource usage without considering cost

C Focus only on reducing upfront capital expenses

D Avoid using any managed cloud services to save money

💡 Hint

Think about balancing cost with service quality.

The Cost Optimization pillar aims to reduce costs while ensuring the system remains performant and reliable. Simply cutting costs without considering impact is not the goal.

❓ Architecture

intermediate

Choosing the Right Storage Class for Cost Savings

You have a data archive that is rarely accessed but must be retained for years. Which AWS storage class is the most cost-effective choice?

A Amazon S3 Intelligent-Tiering

B Amazon S3 Standard

C Amazon S3 Glacier Deep Archive

D Amazon EBS General Purpose SSD

💡 Hint

Consider storage classes designed for long-term, infrequent access.

Amazon S3 Glacier Deep Archive is the lowest-cost storage class for long-term data archiving with infrequent access.

❓ security

advanced

Impact of Cost Optimization on Security

Which cost optimization approach can unintentionally increase security risks in a cloud environment?

A Disabling automated security updates to save costs

B Implementing auto-scaling to match demand

C Using reserved instances for predictable workloads

D Using spot instances for non-critical batch jobs

💡 Hint

Think about what happens if security updates are not applied.

Disabling automated security updates to save money can leave systems vulnerable to attacks, increasing security risks.

❓ service_behavior

advanced

Effect of Auto Scaling on Cost Optimization

How does enabling auto scaling in AWS help optimize costs?

A It keeps all instances running at all times to avoid delays

B It increases instance size to handle peak loads continuously

C It disables unused instances permanently to save cost

D It automatically adjusts the number of instances based on demand

💡 Hint

Consider how resources match workload changes.

Auto scaling adjusts the number of instances dynamically, so you pay only for what you need, reducing waste.

✅ Best Practice

expert

Implementing Cost Allocation Tags

You want to track cloud costs by department and project. Which practice ensures accurate cost allocation in AWS?

A Tag only the resources with the highest cost

B Use cost allocation tags consistently on all resources

C Apply tags randomly to some resources to save time

D Avoid tagging to reduce management overhead

💡 Hint

Think about how to get clear cost reports per group.

Consistent use of cost allocation tags on all resources allows detailed and accurate cost tracking by department and project.

Practice

1. Which AWS tool helps you understand and analyze your cloud spending over time?

easy

A. EC2 Dashboard

B. CloudTrail

C. Cost Explorer

D. IAM

Solution

1. Step 1: Identify AWS tools for cost management

   Cost Explorer is designed to analyze and visualize AWS spending over time.

2. Step 2: Compare other tools' purposes

   CloudTrail tracks API calls, EC2 Dashboard manages instances, IAM manages access, none focus on cost analysis.

3. Final Answer:

   Cost Explorer -> Option C

4. Quick Check:

   Cost analysis tool = Cost Explorer [OK]

Hint: Cost Explorer = spending analysis tool [OK]

Common Mistakes:

• Confusing CloudTrail with cost tool
• Thinking EC2 Dashboard shows costs
• Mixing IAM with billing

2. Which of the following is the correct AWS pricing option to save costs for steady-state workloads?

easy

A. On-Demand Instances

B. Reserved Instances

C. Spot Instances

D. Dedicated Hosts

Solution

1. Step 1: Understand pricing options

   Reserved Instances offer a discount for long-term, steady workloads by committing to usage.

2. Step 2: Compare other options

   On-Demand is pay-as-you-go, Spot is for interruptible workloads, Dedicated Hosts are costly physical servers.

3. Final Answer:

   Reserved Instances -> Option B

4. Quick Check:

   Steady workload savings = Reserved Instances [OK]

Hint: Reserved = save on steady workloads [OK]

Common Mistakes:

• Choosing On-Demand for savings
• Using Spot for steady workloads
• Confusing Dedicated Hosts with cost-saving

3. Consider this AWS Lambda function usage pattern: it runs 1000 times per day, each execution lasts 1 second, and uses 128 MB memory. Which change will reduce cost the most?

medium

A. Increase memory to 512 MB to reduce execution time

B. Decrease memory to 64 MB to save memory cost

C. Increase execution time to batch more work per run

D. Keep memory at 128 MB and reduce execution time by optimizing code

Solution

1. Step 1: Understand Lambda cost factors

   Cost depends on memory size and execution duration multiplied by invocations.

2. Step 2: Evaluate options

   Increasing memory may reduce time but might increase cost; decreasing memory may increase time; optimizing code reduces time without increasing memory.

3. Final Answer:

   Keep memory at 128 MB and reduce execution time by optimizing code -> Option D

4. Quick Check:

   Optimize code to reduce time = save cost [OK]

Hint: Lower execution time saves more than just lowering memory [OK]

Common Mistakes:

• Assuming more memory always saves cost
• Reducing memory without checking time
• Increasing execution time to batch

4. You notice your AWS Trusted Advisor reports underutilized EC2 instances. What is the best immediate action to optimize cost?

medium

A. Resize instances to smaller types matching usage

B. Terminate the underutilized instances immediately

C. Ignore the report as it might be inaccurate

D. Switch all instances to Dedicated Hosts

Solution

1. Step 1: Understand Trusted Advisor recommendations

   It flags underutilized instances to help reduce waste by resizing or terminating.

2. Step 2: Choose best cost optimization action

   Resizing to smaller instances keeps service running but reduces cost; terminating immediately may disrupt service; ignoring wastes money; Dedicated Hosts are expensive.

3. Final Answer:

   Resize instances to smaller types matching usage -> Option A

4. Quick Check:

   Resize underutilized = save cost safely [OK]

Hint: Resize before terminating to avoid downtime [OK]

Common Mistakes:

• Terminating without backup
• Ignoring Trusted Advisor
• Switching to costly Dedicated Hosts

5. A company wants to reduce AWS costs by automating resource scaling and tracking spending. Which combination of AWS services best supports this goal?

hard

A. AWS Auto Scaling + AWS Budgets + AWS Cost Explorer

B. AWS CloudTrail + AWS Config + AWS IAM

C. AWS Lambda + Amazon S3 + Amazon RDS

D. Amazon EC2 + AWS Trusted Advisor + AWS CloudWatch Logs

Solution

1. Step 1: Identify services for automated scaling

   AWS Auto Scaling automatically adjusts resource capacity based on demand.

2. Step 2: Identify services for cost tracking

   AWS Budgets sets spending limits and alerts; Cost Explorer analyzes spending patterns.

3. Step 3: Evaluate other options

   CloudTrail and Config track changes and security, not cost; Lambda, S3, RDS are compute/storage services; Trusted Advisor gives recommendations but not automation; CloudWatch Logs monitor logs.

4. Final Answer:

   AWS Auto Scaling + AWS Budgets + AWS Cost Explorer -> Option A

5. Quick Check:

   Auto scale + budgets + cost explorer = cost optimization [OK]

Hint: Auto Scaling + Budgets + Cost Explorer = automate cost control [OK]

Common Mistakes:

• Confusing CloudTrail with cost tools
• Choosing unrelated services
• Ignoring automation tools