- A
Amazon EMR with EMRFS
EMRFS allows EMR to use S3 as a replacement for HDFS.
- B
Amazon S3
Scalable, durable object storage, ideal for data lakes.
- C
Amazon EBS
Why wrong: Block storage, not suitable for large-scale data lakes.
- D
Amazon FSx for Lustre
Why wrong: High-performance file system, but not as durable or cost-effective as S3 for long-term storage.
- E
Amazon RDS
Why wrong: Relational database, not a storage system for Hadoop workloads.
Question 1,440 of 1,755
MLS-C01 Data Engineering Practice Question
This MLS-C01 practice question tests your understanding of data engineering. 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 data engineering team is migrating on-premises Hadoop workloads to AWS. The workloads include batch processing using Apache Spark and interactive SQL queries. The data is stored in HDFS. Which TWO AWS services should be used to replace HDFS and provide a scalable, durable storage layer? (Choose TWO.)
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
✓
Amazon EMR with EMRFS
Amazon S3 provides a highly durable (99.999999999% durability), scalable, and cost-effective object storage layer that replaces HDFS for Hadoop workloads. Amazon EMR with EMRFS allows Spark and Hive to read and write data directly from S3, treating it as a native filesystem with features like consistent view and read-after-write consistency, making it the ideal compute layer for batch processing and interactive SQL queries.
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.
- ✓
Amazon EMR with EMRFS
Why this is correct
EMRFS allows EMR to use S3 as a replacement for HDFS.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Amazon S3
Why this is correct
Scalable, durable object storage, ideal for data lakes.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon EBS
Why it's wrong here
Block storage, not suitable for large-scale data lakes.
- ✗
Amazon FSx for Lustre
Why it's wrong here
High-performance file system, but not as durable or cost-effective as S3 for long-term storage.
- ✗
Amazon RDS
Why it's wrong here
Relational database, not a storage system for Hadoop workloads.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Amazon EBS or FSx for Lustre as viable HDFS replacements, not realizing that HDFS is a distributed filesystem designed for shared access across many nodes, whereas S3 with EMRFS provides the same semantics with superior durability and scalability.
Detailed technical explanation
How to think about this question
EMRFS implements a Hadoop-compatible filesystem interface that maps S3 objects to HDFS-like paths, using a metadata store (e.g., DynamoDB) to track directory listings and provide consistent listing after write operations. Under the hood, EMRFS leverages S3's multipart upload API for large files and can be configured with server-side encryption (SSE-S3, SSE-KMS, or SSE-C) to meet security requirements. In real-world scenarios, teams often use S3 as the primary data lake with EMRFS for transient clusters, enabling cost savings by spinning up compute only when needed.
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 MLS-C01 question test?
Data Engineering — This question tests Data Engineering — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon EMR with EMRFS — Amazon S3 provides a highly durable (99.999999999% durability), scalable, and cost-effective object storage layer that replaces HDFS for Hadoop workloads. Amazon EMR with EMRFS allows Spark and Hive to read and write data directly from S3, treating it as a native filesystem with features like consistent view and read-after-write consistency, making it the ideal compute layer for batch processing and interactive SQL queries.
What should I do if I get this MLS-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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