AWS Solutions Architect Cost Optimization & Performance 3 — Questions and Answers
Question 1: Which CloudFront feature reduces origin costs by serving cached content to users without hitting the origin server?
- Origin Shield (Correct answer)
- Lambda@Edge
- CloudFront Functions
- Field-Level Encryption
Correct answer: Origin Shield
CloudFront Origin Shield adds a centralized caching layer that increases cache hit ratios and reduces the number of requests forwarded to the origin.
Question 2: A solutions architect needs to process millions of small tasks asynchronously at the lowest possible cost. Which compute option is best?
- EC2 On-Demand
- AWS Lambda (Correct answer)
- EC2 Reserved Instances
- AWS Fargate
Correct answer: AWS Lambda
AWS Lambda charges only for actual compute time in millisecond increments with no idle costs, making it ideal for infrequent or short-duration tasks.
Question 3: Which DynamoDB capacity mode eliminates the need to provision throughput and is cost-effective for unpredictable traffic?
- Provisioned mode with Auto Scaling
- On-Demand mode (Correct answer)
- Global Tables mode
- DAX-accelerated mode
Correct answer: On-Demand mode
DynamoDB On-Demand mode charges per request and automatically handles any traffic level without capacity planning.
Question 4: An application stores large media files in S3. Users frequently request the same files from multiple regions. What reduces both latency and data transfer costs?
- S3 Cross-Region Replication
- Amazon CloudFront distribution (Correct answer)
- S3 Transfer Acceleration
- S3 Multi-Region Access Points
Correct answer: Amazon CloudFront distribution
CloudFront caches content at edge locations globally, reducing repeated origin fetches and lowering both latency and data transfer out costs from S3.
Question 5: Which EC2 pricing model is best for a steady-state 24/7 production database that must run for 3 years?
- On-Demand Instances
- Spot Instances
- 3-year Reserved Instances (All Upfront) (Correct answer)
- Savings Plans
Correct answer: 3-year Reserved Instances (All Upfront)
3-year All Upfront Reserved Instances provide the maximum discount (~72%) for predictable, always-on workloads.
Question 6: A company wants to reduce RDS costs for a dev/test database that is only used 8 hours per day. What is the most cost-effective approach?
- Use RDS Multi-AZ for lower pricing
- Stop the RDS instance when not in use (Correct answer)
- Switch to Aurora Serverless v1
- Use smaller instance class
Correct answer: Stop the RDS instance when not in use
Stopping an RDS instance halts compute charges while retaining storage, saving ~67% for an 8-hour/day database compared to running 24/7.
Question 7: Which AWS service helps identify idle and underutilized EC2 instances to reduce unnecessary spending?
- Amazon Inspector
- AWS Cost Anomaly Detection
- AWS Trusted Advisor (Correct answer)
- Amazon GuardDuty
Correct answer: AWS Trusted Advisor
AWS Trusted Advisor's cost optimization checks identify low-utilization EC2 instances based on CPU and network usage over a 14-day period.
AWS Solutions Architect Cost Optimization & Performance 3
Which CloudFront feature reduces origin costs by serving cached content to users without hitting the origin server?