- A
Use AWS Lambda with Provisioned Concurrency for Service B and keep Service C as a Fargate service.
Why wrong: Provisioned Concurrency adds cost; Service C should be serverless to reduce idle cost.
- B
Use a step scaling policy for Service B based on CPU utilization and keep Service C as is.
Why wrong: CPU utilization may not reflect queue backlog; Service C remains idle costing money.
- C
Configure Service B with a target tracking scaling policy based on the SQS queue backlog and convert Service C to an AWS Lambda function triggered by DynamoDB Streams.
Target tracking scaling based on SQS backlog scales Service B appropriately; Lambda for Service C eliminates idle cost.
- D
Increase the number of ECS tasks for Service B manually and use a scheduled scaling policy for Service C.
Why wrong: Manual scaling does not handle variable traffic; scheduled scaling is not suitable for idle service.
Quick Answer
The correct solution is to configure Service B with a target tracking scaling policy based on the SQS queue backlog and convert Service C to an AWS Lambda function triggered by DynamoDB Streams. This approach directly addresses the cost optimization and scaling challenges for ECS with Fargate by using the SQS backlog metric—specifically ApproximateNumberOfMessagesVisible—to drive precise, demand-based scaling for Service B, eliminating the lag observed during load tests. Converting Service C to Lambda removes the idle compute costs of a perpetually running Fargate task, as Lambda executes only when DynamoDB Streams detects new records, aligning perfectly with variable traffic patterns. On the SAP-C02 exam, this scenario tests your ability to differentiate between reactive scaling policies and proactive, metric-driven scaling, as well as recognizing when serverless architectures like Lambda are more cost-effective than containerized services for event-driven workloads. A common trap is choosing a simple CPU-based scaling policy for Service B, which fails to correlate with actual work demand. Memory tip: “Backlog beats CPU” for scaling, and “Streams slash idle costs” for converting idle services.
SAP-C02 Design for New Solutions Practice Question
This SAP-C02 practice question tests your understanding of design for new solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is designing a new application that will run on Amazon ECS with Fargate. The application consists of three microservices: Service A, Service B, and Service C. Service A receives HTTP requests from an Application Load Balancer and sends messages to an Amazon SQS queue. Service B polls the SQS queue and processes the messages, storing results in Amazon DynamoDB. Service C reads from DynamoDB and sends notifications via Amazon SNS. The company expects variable traffic and wants to minimize costs. During a load test, the team observes that Service B is not scaling fast enough, causing the SQS queue to grow. The team also notices that Service C is idle most of the time. Which solution should the company implement to improve scaling and reduce costs?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Configure Service B with a target tracking scaling policy based on the SQS queue backlog and convert Service C to an AWS Lambda function triggered by DynamoDB Streams.
Option C is correct because it addresses both scaling and cost issues: Service B's scaling is improved by using a target tracking scaling policy based on the SQS queue backlog (ApproximateNumberOfMessagesVisible), which directly correlates to the work demand, ensuring faster and more precise scaling. Converting Service C to a Lambda function triggered by DynamoDB Streams eliminates idle compute costs from a constantly running Fargate service, as Lambda only runs when new data appears in DynamoDB, reducing costs significantly.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use AWS Lambda with Provisioned Concurrency for Service B and keep Service C as a Fargate service.
Why it's wrong here
Provisioned Concurrency adds cost; Service C should be serverless to reduce idle cost.
- ✗
Use a step scaling policy for Service B based on CPU utilization and keep Service C as is.
Why it's wrong here
CPU utilization may not reflect queue backlog; Service C remains idle costing money.
- ✓
Configure Service B with a target tracking scaling policy based on the SQS queue backlog and convert Service C to an AWS Lambda function triggered by DynamoDB Streams.
Why this is correct
Target tracking scaling based on SQS backlog scales Service B appropriately; Lambda for Service C eliminates idle cost.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the number of ECS tasks for Service B manually and use a scheduled scaling policy for Service C.
Why it's wrong here
Manual scaling does not handle variable traffic; scheduled scaling is not suitable for idle service.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose CPU-based scaling (Option B) because it is familiar, but they fail to recognize that queue depth is a more direct and responsive metric for scaling message-processing services, and they overlook the cost savings of replacing an idle Fargate service with a Lambda function triggered by DynamoDB Streams.
Detailed technical explanation
How to think about this question
The target tracking scaling policy for Service B uses the SQS queue's ApproximateNumberOfMessagesVisible metric, which is a direct measure of backlog; the ECS service auto-scales to maintain a target value (e.g., 100 messages per task), ensuring rapid response to traffic spikes. DynamoDB Streams capture item-level changes in near real-time, and Lambda functions can be triggered synchronously with a batch size and window, allowing Service C to process only when new data exists, with no idle compute cost. This pattern is commonly used in event-driven architectures to replace polling-based services, reducing both latency and cost.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this SAP-C02 question test?
Design for New Solutions — This question tests Design for New Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure Service B with a target tracking scaling policy based on the SQS queue backlog and convert Service C to an AWS Lambda function triggered by DynamoDB Streams. — Option C is correct because it addresses both scaling and cost issues: Service B's scaling is improved by using a target tracking scaling policy based on the SQS queue backlog (ApproximateNumberOfMessagesVisible), which directly correlates to the work demand, ensuring faster and more precise scaling. Converting Service C to a Lambda function triggered by DynamoDB Streams eliminates idle compute costs from a constantly running Fargate service, as Lambda only runs when new data appears in DynamoDB, reducing costs significantly.
What should I do if I get this SAP-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This SAP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAP-C02 exam.
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