The answer is index fragmentation, and the solution is to rebuild or reorganize the indexes. This is correct because over months of insert, update, and delete operations, the logical order of index pages becomes misaligned with the physical order on disk, forcing the query engine to perform inefficient index scans instead of seeks. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of SQL Server index fragmentation performance and how it manifests in Cloud SQL for SQL Server—a common trap is assuming you need more storage or a larger machine, when the real fix is index maintenance. Remember the memory tip: “Scans mean fragmentation, not capacity limitation.”
PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. 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 Cloud SQL for SQL Server instance has been running for months. Recently, the database size grew significantly and now query performance has degraded. The DBA checks the query execution plan and sees index scans. The current storage is 500GB SSD. What is the most likely cause and solution?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Index fragmentation; rebuild or reorganize indexes
The correct answer is B. Index fragmentation occurs over time as data is inserted, updated, or deleted, causing indexes to become inefficient. The query execution plan showing index scans (instead of seeks) is a classic symptom of fragmented indexes. Rebuilding or reorganizing the indexes will defragment them, restoring query performance without requiring additional storage or infrastructure changes.
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.
✗
Increase storage capacity to 1TB SSD
Why it's wrong here
More storage doesn't reduce fragmentation.
✓
Index fragmentation; rebuild or reorganize indexes
Why this is correct
Index fragmentation increases scan cost; rebuilding reorganizes data pages.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Enable query insights to analyze performance
Why it's wrong here
Query insights diagnose but do not solve; indexing needs action.
✗
Enable read replicas to offload queries
Why it's wrong here
Read replicas reduce load but do not fix root cause of slow scans.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that performance degradation from data growth is always a storage capacity issue, leading candidates to choose a storage increase instead of recognizing index fragmentation as the root cause when execution plans show index scans.
Detailed technical explanation
How to think about this question
Index fragmentation occurs when the logical order of index pages does not match the physical order on disk, often due to page splits during data modifications. The SQL Server index rebuild operation (ALTER INDEX ... REBUILD) drops and recreates the index, compacting pages and reordering them physically, while reorganizing (ALTER INDEX ... REORGANIZE) defragments the leaf level. In Cloud SQL for SQL Server, the DBA can run these commands directly, and the operation is logged and can be scheduled during maintenance windows to minimize impact.
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.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Index fragmentation; rebuild or reorganize indexes — The correct answer is B. Index fragmentation occurs over time as data is inserted, updated, or deleted, causing indexes to become inefficient. The query execution plan showing index scans (instead of seeks) is a classic symptom of fragmented indexes. Rebuilding or reorganizing the indexes will defragment them, restoring query performance without requiring additional storage or infrastructure changes.
What should I do if I get this PCDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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