- A
Amazon EBS
Why wrong: An EBS volume can only be attached to a single EC2 instance at a time (except for EBS Multi-Attach, which is limited to specific volume types and use cases). It is not designed for simultaneous shared access across multiple instances.
- B
Instance Store
Why wrong: Instance Store is local temporary storage tied to a single EC2 instance. It cannot be shared across instances.
- C
Amazon EFS
EFS provides a shared NFS file system that can be mounted simultaneously by multiple EC2 instances across multiple AZs. It scales automatically and supports concurrent reads and writes from many instances.
- D
Amazon S3
Why wrong: S3 can be used to share files but is accessed via API calls, not mounted as a native file system. For applications that require a mounted file system interface with shared access, EFS is the correct service.
CLF-C02 Cloud Technology and Services Practice Question
This CLF-C02 practice question tests your understanding of cloud technology and services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 runs a web application on multiple EC2 instances across multiple Availability Zones. All instances need to access and share the same file system simultaneously to read and write shared configuration files. Which AWS storage service supports simultaneous access from multiple EC2 instances?
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 EFS
Amazon EFS is a fully managed, NFS-based file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones, providing shared access for reading and writing configuration files. It uses the NFSv4.1 protocol and supports thousands of simultaneous connections, making it ideal for shared storage scenarios.
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 EBS
Why it's wrong here
An EBS volume can only be attached to a single EC2 instance at a time (except for EBS Multi-Attach, which is limited to specific volume types and use cases). It is not designed for simultaneous shared access across multiple instances.
- ✗
Instance Store
Why it's wrong here
Instance Store is local temporary storage tied to a single EC2 instance. It cannot be shared across instances.
- ✓
Amazon EFS
Why this is correct
EFS provides a shared NFS file system that can be mounted simultaneously by multiple EC2 instances across multiple AZs. It scales automatically and supports concurrent reads and writes from many instances.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon S3
Why it's wrong here
S3 can be used to share files but is accessed via API calls, not mounted as a native file system. For applications that require a mounted file system interface with shared access, EFS is the correct service.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse Amazon EBS with a shared file system, not realizing that standard EBS volumes are single-instance attachable, while EFS is purpose-built for multi-instance shared access.
Detailed technical explanation
How to think about this question
Amazon EFS implements a distributed file system using NFSv4.1 with support for file locking and consistency semantics, allowing multiple EC2 instances to read and write the same files concurrently. Under the hood, EFS data is stored across multiple Availability Zones within a region, providing high durability and availability, and performance scales automatically with storage size. A real-world scenario is a web application cluster where all instances need to share a common configuration directory or session state, which EFS handles seamlessly without requiring application changes.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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 CLF-C02 question test?
Cloud Technology and Services — This question tests Cloud Technology and Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Amazon EFS — Amazon EFS is a fully managed, NFS-based file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones, providing shared access for reading and writing configuration files. It uses the NFSv4.1 protocol and supports thousands of simultaneous connections, making it ideal for shared storage scenarios.
What should I do if I get this CLF-C02 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: Jun 11, 2026
This CLF-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 CLF-C02 exam.
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