- A
Increase the instance type size
Why wrong: Larger instances may speed up processing but do not reduce idle time at start.
- B
Use Spot Instances for all nodes
Why wrong: Spot instances can be reclaimed, causing job failures; not suitable for production.
- C
Configure a larger initial core instance count and enable managed scaling
More core nodes reduce the time to allocate resources, and managed scaling adjusts during the job.
- D
Purchase Reserved Instances for the cluster
Why wrong: Reserved Instances are cost-effective for steady-state, not for transient clusters.
Question 1,506 of 1,786
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 data engineer is using Amazon EMR to transform large datasets stored in S3. The cluster runs once a day and takes 3 hours. The engineer notices that the cluster is idle for 30 minutes at the start while waiting for resources. What is the most cost-effective way to reduce the idle time?
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 a larger initial core instance count and enable managed scaling
Option C is correct because enabling managed scaling allows the EMR cluster to automatically adjust its core instance count based on workload demands, reducing the initial idle time caused by waiting for resource allocation. By configuring a larger initial core instance count, the cluster can start processing immediately with sufficient capacity, and managed scaling then optimizes resource usage throughout the job, making it the most cost-effective solution for a daily 3-hour transformation job.
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.
- ✗
Increase the instance type size
Why it's wrong here
Larger instances may speed up processing but do not reduce idle time at start.
- ✗
Use Spot Instances for all nodes
Why it's wrong here
Spot instances can be reclaimed, causing job failures; not suitable for production.
- ✓
Configure a larger initial core instance count and enable managed scaling
Why this is correct
More core nodes reduce the time to allocate resources, and managed scaling adjusts during the job.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Purchase Reserved Instances for the cluster
Why it's wrong here
Reserved Instances are cost-effective for steady-state, not for transient clusters.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse cost optimization strategies (like Spot Instances or Reserved Instances) with performance improvements, failing to recognize that idle time at startup is a resource allocation issue best solved by managed scaling and initial capacity configuration.
Detailed technical explanation
How to think about this question
Managed scaling in EMR uses a dynamic scaling policy based on metrics like YARN memory or vCPU utilization to adjust core and task instance counts in near real-time. The initial idle time often stems from the time required to provision and bootstrap EC2 instances; by setting a larger initial core count, the cluster can begin processing while additional instances are launched asynchronously. In practice, this approach is especially effective for bursty workloads where the cluster must quickly scale up to handle a spike in data processing, such as daily ETL jobs that process terabytes of data from S3.
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.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure a larger initial core instance count and enable managed scaling — Option C is correct because enabling managed scaling allows the EMR cluster to automatically adjust its core instance count based on workload demands, reducing the initial idle time caused by waiting for resource allocation. By configuring a larger initial core instance count, the cluster can start processing immediately with sufficient capacity, and managed scaling then optimizes resource usage throughout the job, making it the most cost-effective solution for a daily 3-hour transformation job.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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