- A
Amazon EBS
Why wrong: EBS volumes attach to one EC2 instance at a time and are not designed for shared multi-instance file access.
- B
Amazon EFS
Amazon EFS is a managed shared file system that can be mounted by multiple EC2 instances across multiple Availability Zones. It is a strong fit when applications need the same files at the same time and must remain available even if one AZ experiences issues. The service is highly available by design and reduces operational work compared with self-managed file servers.
- C
Amazon S3 only
Why wrong: S3 is object storage, not a mounted shared file system for POSIX-style file access.
- D
Instance store
Why wrong: Instance store is ephemeral and tied to the lifecycle of the instance, so it is not durable shared storage.
SAA-C03 Design Secure Architectures Practice Question
This SAA-C03 practice question tests your understanding of design secure architectures. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Several EC2 instances in different Availability Zones need to read and write the same shared file system. The file storage should stay available if one AZ has a problem. Which service should the team choose?
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 provides a fully managed, scalable, and elastic NFS file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones. It is designed for high availability and durability by storing data redundantly across multiple AZs within a region, ensuring continued access even if one AZ fails.
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
EBS volumes attach to one EC2 instance at a time and are not designed for shared multi-instance file access.
When this WOULD be correct
A single EC2 instance needs a durable, block-level storage volume with consistent low latency, and the workload does not require multi-instance access or cross-AZ resilience. For example, a database server's data volume.
- ✓
Amazon EFS
Why this is correct
Amazon EFS is a managed shared file system that can be mounted by multiple EC2 instances across multiple Availability Zones. It is a strong fit when applications need the same files at the same time and must remain available even if one AZ experiences issues. The service is highly available by design and reduces operational work compared with self-managed file servers.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Amazon S3 only
Why it's wrong here
S3 is object storage, not a mounted shared file system for POSIX-style file access.
When this WOULD be correct
When the requirement is to store and retrieve large amounts of unstructured data (e.g., images, videos, backups) from multiple EC2 instances, and the application uses S3 SDK or REST API rather than a mounted file system. Also correct for static website hosting or data lake scenarios.
- ✗
Instance store
Why it's wrong here
Instance store is ephemeral and tied to the lifecycle of the instance, so it is not durable shared storage.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Amazon EFSCorrect answer▾
Why this is correct
Amazon EFS is a managed shared file system that can be mounted by multiple EC2 instances across multiple Availability Zones. It is a strong fit when applications need the same files at the same time and must remain available even if one AZ experiences issues. The service is highly available by design and reduces operational work compared with self-managed file servers.
✗Amazon EBSWrong answer — click to see why▾
Why this is wrong here
Amazon EBS volumes are tied to a single Availability Zone and cannot be shared across multiple EC2 instances in different AZs, so they cannot provide the required shared file system with cross-AZ availability.
★ When this WOULD be the correct answer
A single EC2 instance needs a durable, block-level storage volume with consistent low latency, and the workload does not require multi-instance access or cross-AZ resilience. For example, a database server's data volume.
Why candidates choose this
Candidates may confuse EBS with a shared file system because EBS volumes can be attached to one instance at a time, but they overlook the multi-AZ and multi-instance sharing requirements.
✗Amazon S3 onlyWrong answer — click to see why▾
Why this is wrong here
Amazon S3 is object storage, not a shared file system; EC2 instances cannot mount S3 as a POSIX-compliant file system for concurrent read/write access. It also does not provide file locking or low-latency file operations needed for shared file systems.
★ When this WOULD be the correct answer
When the requirement is to store and retrieve large amounts of unstructured data (e.g., images, videos, backups) from multiple EC2 instances, and the application uses S3 SDK or REST API rather than a mounted file system. Also correct for static website hosting or data lake scenarios.
Why candidates choose this
Candidates may think S3 is highly available and durable, and assume it can serve as a shared file system because it is accessible from any instance, overlooking the lack of file system semantics like locking and POSIX compliance.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse EBS Multi-Attach (which only supports a limited number of instances in the same AZ and requires a cluster-aware file system) with the true multi-AZ shared file system capability of EFS.
Detailed technical explanation
How to think about this question
EFS uses the NFSv4.1 protocol and leverages a distributed data plane to automatically replicate file data across multiple AZs within a region, providing 99.999999999% (11 nines) durability. Under the hood, EFS employs a file system metadata layer and a data storage layer that scales elastically as files are added or removed, with performance modes (General Purpose and Max I/O) and throughput modes (Bursting and Provisioned) to suit different workload patterns. In a real-world scenario, a containerized application using EFS can persist shared configuration files or logs across a fleet of EC2 instances in different AZs, surviving an AZ outage without manual intervention.
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.
What to study next
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FAQ
Questions learners often ask
What does this SAA-C03 question test?
Design Secure Architectures — This question tests Design Secure Architectures — 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 provides a fully managed, scalable, and elastic NFS file system that can be mounted concurrently by multiple EC2 instances across different Availability Zones. It is designed for high availability and durability by storing data redundantly across multiple AZs within a region, ensuring continued access even if one AZ fails.
What should I do if I get this SAA-C03 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
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