Multiple EC2 instances need a shared filesystem so they can concurrently read and write the same files (for example, user uploads and rendered assets). The instances are in different Availability Zones and must mount the filesystem using NFS. Which AWS storage service best fits?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
Best answer
Amazon EFS
EFS provides a shared, NFS-compatible filesystem that supports mounting from multiple EC2 instances and AZs.
Distractor review
Amazon S3
S3 is object storage and does not provide native shared POSIX/NFS filesystem semantics for concurrent writes.
Distractor review
Amazon EBS gp3 volumes
EBS volumes are tied to a single Availability Zone and cannot be mounted as a shared filesystem across AZs.
Distractor review
Instance store on EC2
Instance store is ephemeral and not suitable for a shared, concurrently written filesystem requirement.
Common exam trap
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Technical deep dive
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A team needs to distribute TCP traffic (not HTTP) across multiple services. The services must see the original client source IP for auditing. Which AWS load balancer is the best fit?
Question 2
A team wants to run containerized services with AWS-managed orchestration and autoscaling. They do NOT require Kubernetes compatibility. Which AWS service choice is most appropriate to meet these goals?
Question 3
A solutions architect is designing an S3 bucket for a IoT ingestion API. The objects must never be publicly accessible, even if a developer later adds an overly broad bucket policy. What should the architect configure? The design must avoid adding custom operational scripts.
Question 4
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Question 5
A team wants to delegate IAM management to developers, but must ensure developers can never grant themselves permissions beyond a specific limit. Which AWS mechanism best matches this requirement?
Question 6
A solutions architect is designing an S3 bucket for a healthcare document service. The objects must never be publicly accessible, even if a developer later adds an overly broad bucket policy. What should the architect configure?
FAQ
Questions learners often ask
What does this SAA-C03 question test?
Static NAT maps one inside address to one outside address.
What is the correct answer to this question?
The correct answer is: Amazon EFS — Amazon EFS is designed for exactly this pattern: a shared filesystem that is NFS-compatible and can be mounted by multiple EC2 instances, including instances in different Availability Zones. That enables concurrent access to the same directory structure and files without implementing your own synchronization layer. In contrast, S3 is object storage with a different access model and does not behave like an NFS shared filesystem for concurrent POSIX-style operations. EBS volumes are AZ-scoped and cannot be shared across AZs as a single mounted filesystem. S3 does not provide native NFS shared filesystem semantics for concurrent reads/writes, so applications expecting a filesystem mount would not work directly. EBS is bound to one Availability Zone, preventing a shared mount across multiple AZs. Instance store is ephemeral and also not shared as a reliable cross-instance filesystem.
What should I do if I get this SAA-C03 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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