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Operations and Maintenance →hardMultiple ChoiceObjective-mapped

PAS-C01 Operations and Maintenance Practice Question

This PAS-C01 practice question tests your understanding of operations and maintenance. 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.

A company runs a multi-tier application on AWS. The application consists of an Application Load Balancer (ALB) that distributes traffic to a fleet of EC2 instances running a web server. The web servers write logs to an Amazon EFS file system mounted across all instances. The operations team reports that the web application is experiencing intermittent high latency and timeouts. Monitoring shows that the ALB's target response time is normal, but the application's internal processing time is high. Further investigation reveals that the EFS performance metrics show high 'BurstCreditBalance' and 'PercentIOLimit' during the latency spikes. The EFS file system is configured with 'Bursting' throughput mode. The team needs to resolve the latency issue with minimal cost. What should they do?

A
Migrate the log files to Amazon S3 and use S3 Transfer Acceleration for writes.
Why wrong: S3 is not a POSIX-compliant file system; rewriting applications to use S3 is costly and complex.
B
Switch the EFS throughput mode to Provisioned Throughput to guarantee higher performance.
Why wrong: Provisioned Throughput incurs higher cost; increasing file system size is more cost-effective if baseline throughput suffices.
C
Add more EC2 instances to the Auto Scaling group to distribute the I/O load.
Why wrong: More instances increase concurrent I/O, potentially worsening the bottleneck.
D
Increase the size of the EFS file system to increase the baseline throughput and burst credits.
Larger EFS file systems have higher baseline throughput and accumulate more burst credits, reducing I/O wait.

Full breakdown with real-world context →

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

✓

Increase the size of the EFS file system to increase the baseline throughput and burst credits.

Option D is correct because increasing the size of an EFS file system in Bursting mode raises its baseline throughput and burst credit accumulation rate. The high BurstCreditBalance and PercentIOLimit indicate the file system is exhausting its burst credits and hitting its I/O limit, causing throttling and latency. A larger EFS volume provides a higher baseline throughput, reducing reliance on burst credits and smoothing performance without additional cost for Provisioned Throughput.

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.

✗
Migrate the log files to Amazon S3 and use S3 Transfer Acceleration for writes.
Why it's wrong here
S3 is not a POSIX-compliant file system; rewriting applications to use S3 is costly and complex.
✗
Switch the EFS throughput mode to Provisioned Throughput to guarantee higher performance.
Why it's wrong here
Provisioned Throughput incurs higher cost; increasing file system size is more cost-effective if baseline throughput suffices.
✗
Add more EC2 instances to the Auto Scaling group to distribute the I/O load.
Why it's wrong here
More instances increase concurrent I/O, potentially worsening the bottleneck.
✓
Increase the size of the EFS file system to increase the baseline throughput and burst credits.
Why this is correct
Larger EFS file systems have higher baseline throughput and accumulate more burst credits, reducing I/O wait.
Related concept
Read the scenario before looking for a memorised answer.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume 'Bursting' mode is always sufficient and look to add compute capacity (Option C) or change storage type (Option A), when the real issue is that the file system is too small to sustain the workload's I/O demands, and resizing it is the most cost-effective fix.

Detailed technical explanation

How to think about this question

EFS Bursting mode uses a credit bucket that refills at a baseline rate proportional to the file system's size (50 MiB/s per TiB of storage). When the workload exceeds this baseline, it consumes burst credits; once credits are depleted, throughput is throttled to the baseline, causing latency spikes. Increasing the file system size directly raises both the baseline throughput and the rate at which burst credits accumulate, effectively increasing the sustainable I/O capacity without changing the throughput mode.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this PAS-C01 question test?

Operations and Maintenance — This question tests Operations and Maintenance — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Increase the size of the EFS file system to increase the baseline throughput and burst credits. — Option D is correct because increasing the size of an EFS file system in Bursting mode raises its baseline throughput and burst credit accumulation rate. The high BurstCreditBalance and PercentIOLimit indicate the file system is exhausting its burst credits and hitting its I/O limit, causing throttling and latency. A larger EFS volume provides a higher baseline throughput, reducing reliance on burst credits and smoothing performance without additional cost for Provisioned Throughput.

What should I do if I get this PAS-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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This PAS-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 PAS-C01 exam.