Quick Answer
The answer is Amazon Elastic File System (Amazon EFS), the correct choice for shared file storage accessed by multiple EC2 instances. EFS provides a fully managed NFS file system that supports concurrent access from thousands of EC2 instances across multiple Availability Zones, automatically replicating data within a region to achieve 11 nines of durability. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your ability to distinguish between block, object, and file storage services—a common trap is confusing EBS (which is block storage attached to a single instance) with EFS. Remember that EBS is like a direct-attached hard drive, while EFS is a network drive that multiple instances can mount simultaneously. For the exam, a quick memory tip: “EFS = Elastic File System = Everyone’s File System,” reinforcing its multi-instance, multi-AZ shared access capability.
This DEA-C01 practice question tests your understanding of data store management. 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 needs to store files that are accessed by multiple EC2 instances in a VPC. The files must be concurrently accessible and durable. Which storage solution should the data engineer choose?
Amazon EC2 instance store
Why wrong: Instance store is ephemeral and not durable.
Amazon Simple Storage Service (Amazon S3)
Why wrong: S3 is object storage, not a file system.
Amazon Elastic Block Store (Amazon EBS)
Why wrong: EBS volumes cannot be attached to multiple instances concurrently.
Amazon Elastic File System (Amazon EFS)
EFS provides a shared, durable file system for EC2 instances.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Amazon Elastic File System (Amazon EFS)
Amazon EFS provides a fully managed, scalable, and elastic NFS file system that can be concurrently accessed by multiple EC2 instances across multiple Availability Zones. It is designed for high durability (11 nines of durability) and automatically replicates data across multiple AZs within a region, meeting the requirements for concurrent access and durability.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Amazon EC2 instance store
Why it's wrong here
Instance store is ephemeral and not durable.
Amazon Simple Storage Service (Amazon S3)
Why it's wrong here
S3 is object storage, not a file system.
Amazon Elastic Block Store (Amazon EBS)
Why it's wrong here
EBS volumes cannot be attached to multiple instances concurrently.
Amazon Elastic File System (Amazon EFS)
Why this is correct
EFS provides a shared, durable file system for EC2 instances.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse Amazon EBS Multi-Attach with a general-purpose shared file system, but EBS Multi-Attach is limited to specific io1/io2 volumes, requires cluster-aware applications, and does not provide the POSIX file system semantics or cross-AZ durability that EFS offers.
Detailed technical explanation
EFS uses the NFSv4.1 protocol and provides a POSIX-compliant file system interface, allowing multiple EC2 instances to read and write the same files concurrently with strong consistency. Under the hood, EFS distributes file data across multiple AZs using a distributed data store, and its performance modes (General Purpose and Max I/O) allow scaling throughput and IOPS based on the amount of data stored. A real-world scenario is a web application serving static assets from a shared file system across a fleet of EC2 instances behind a load balancer, where EFS ensures all instances see the same files without manual replication.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
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Data Store Management — study guide chapter
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FAQ
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
The correct answer is: Amazon Elastic File System (Amazon EFS) — Amazon EFS provides a fully managed, scalable, and elastic NFS file system that can be concurrently accessed by multiple EC2 instances across multiple Availability Zones. It is designed for high durability (11 nines of durability) and automatically replicates data across multiple AZs within a region, meeting the requirements for concurrent access and durability.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This DEA-C01 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 DEA-C01 exam.
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