The correct answer is to modify the DB instance to increase the allocated storage size and to enable storage auto scaling. These two actions resolve the issue of increasing RDS storage without downtime because Amazon RDS for PostgreSQL supports online storage scaling, meaning the storage modification takes effect dynamically while the database remains fully available for reads and writes. Storage auto scaling further eliminates manual intervention by automatically adding storage when thresholds are breached, preventing out-of-space errors. On the AWS Certified DevOps Engineer Professional DOP-C02 exam, this scenario tests your understanding of RDS storage management under the “High Availability and Fault Tolerance” domain, often appearing as a distractor against snapshot-based resizing or instance class modifications, which do cause downtime. A common trap is assuming you must stop the instance to modify storage, but PostgreSQL on RDS allows live modifications. Memory tip: think “Live Scale” for PostgreSQL — both manual and auto scaling are online operations, while other engines like SQL Server may require downtime.
DOP-C02 Incident and Event Response Practice Question
This DOP-C02 practice question tests your understanding of incident and event response. 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 DevOps engineer is troubleshooting an Amazon RDS for PostgreSQL instance that is running out of storage. The engineer wants to resolve the issue without downtime. Which TWO actions can achieve this? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable storage auto scaling on the DB instance.
Option B is correct because enabling storage auto scaling on an Amazon RDS for PostgreSQL instance allows the database to automatically increase its allocated storage when it detects that available storage is running low, preventing out-of-storage errors without requiring manual intervention or downtime. Option E is correct because modifying the DB instance to increase the allocated storage size is a dynamic operation that can be performed without downtime, as Amazon RDS supports online storage scaling for PostgreSQL instances, allowing the change to take effect while the database remains available.
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.
✗
Create a read replica and promote it to primary.
Why it's wrong here
This does not increase storage on the original instance.
✓
Enable storage auto scaling on the DB instance.
Why this is correct
Auto scaling adds storage automatically without manual intervention.
Related concept
Read the scenario before looking for a memorised answer.
✗
Delete old automated snapshots to free up storage.
Why it's wrong here
Automated snapshots do not consume the instance's allocated storage.
✗
Scale up the DB instance to a larger instance class.
Why it's wrong here
Instance class does not affect storage.
✓
Modify the DB instance to increase the allocated storage size.
Why this is correct
Modifying storage can be done with minimal downtime.
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 often confuse instance class scaling (compute/memory) with storage scaling, or mistakenly think that deleting snapshots (which are stored separately in S3) can free up space on the DB instance's attached storage volume.
Detailed technical explanation
How to think about this question
Amazon RDS storage auto scaling works by monitoring the free storage space on the DB instance; when free space falls below a threshold (typically 10% of allocated storage or less than 200 GB), it automatically increases storage in increments based on the current allocation, up to the maximum limit for the instance class. For PostgreSQL, modifying the allocated storage size is a non-disruptive operation because RDS performs the modification in the background, and the instance remains available throughout the process, though a brief performance impact may occur during the storage reconfiguration. In real-world scenarios, storage auto scaling is particularly useful for unpredictable workloads, such as applications with seasonal spikes in data ingestion, where manual monitoring would be impractical.
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
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.
Incident and Event Response — This question tests Incident and Event Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Enable storage auto scaling on the DB instance. — Option B is correct because enabling storage auto scaling on an Amazon RDS for PostgreSQL instance allows the database to automatically increase its allocated storage when it detects that available storage is running low, preventing out-of-storage errors without requiring manual intervention or downtime. Option E is correct because modifying the DB instance to increase the allocated storage size is a dynamic operation that can be performed without downtime, as Amazon RDS supports online storage scaling for PostgreSQL instances, allowing the change to take effect while the database remains available.
What should I do if I get this DOP-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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. An Amazon RDS for PostgreSQL instance is running low on storage. The DevOps engineer needs to increase the allocated storage without downtime. Which action should be taken?
easy
A.Modify the DB instance to a larger instance class.
✓ B.Modify the DB instance to increase the allocated storage.
C.Create a snapshot of the DB instance and restore it with larger storage.
D.Launch a new read replica with larger storage and promote it.
Why B: Option B is correct because RDS supports modifying storage settings without downtime; the change is applied during the next maintenance window or immediately if the 'Apply Immediately' option is selected. Option A is wrong because taking a snapshot and restoring would cause downtime. Option C is wrong because you cannot add storage to an existing instance in a different way; you must modify the DB instance. Option D is wrong because modifying the DB instance class does not increase storage.
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This DOP-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 DOP-C02 exam.
Question Discussion
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