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PCDOE Manage Database Solutions Practice Question

Q: How is Manage Database Solutions tested on the PCDOE exam?

Manage Database Solutions — This question tests Manage Database Solutions — Read the scenario before looking for a memorised answer..

Q: What is the correct answer to this Manage Database Solutions PCDOE question?

The correct answer is: The query is using an inequality filter on 'created_date' which requires a composite index. — In Firestore Native mode, queries that apply an inequality filter (e.g., >=, >, <, !=) on a field automatically require a composite index on both the equality filter field and the inequality filter field to avoid a full collection scan. Without that composite index, Firestore performs a back-end scan of all documents matching the equality filter, then applies the inequality filter in memory, resulting in high document reads. Option A correctly identifies that the inequality filter on 'created_date' is the most likely cause of the excessive reads because it forces Firestore to read and discard many documents that do not satisfy the timestamp condition.

Q: Why do candidates get Manage Database Solutions questions wrong on the PCDOE exam?

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

This PCDOE practice question tests your understanding of manage database solutions. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.

An application uses Firestore in Native mode. The query filters on two fields: 'status' (string) and 'created_date' (timestamp). The query returns results but the billing shows high document reads. What is the most likely cause?

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.

A
The query is using an inequality filter on 'created_date' which requires a composite index.
Correct. Queries with equality on one field and inequality on another need a composite index to avoid scanning all documents.
B
The query is using 'array-contains' which always scans the entire collection.
Why wrong: array-contains can use existing indexes if properly indexed.
C
The 'status' field is not indexed because single-field indexes are not automatic.
Why wrong: Single-field indexes are automatic in Native mode.
D
The query is missing an ORDER BY clause causing a full scan.
Why wrong: Missing ORDER BY does not cause a full scan if indexes are used.

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

✓

The query is using an inequality filter on 'created_date' which requires a composite index.

In Firestore Native mode, queries that apply an inequality filter (e.g., >=, >, <, !=) on a field automatically require a composite index on both the equality filter field and the inequality filter field to avoid a full collection scan. Without that composite index, Firestore performs a back-end scan of all documents matching the equality filter, then applies the inequality filter in memory, resulting in high document reads. Option A correctly identifies that the inequality filter on 'created_date' is the most likely cause of the excessive reads because it forces Firestore to read and discard many documents that do not satisfy the timestamp condition.

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.

✓
The query is using an inequality filter on 'created_date' which requires a composite index.
Why this is correct
Correct. Queries with equality on one field and inequality on another need a composite index to avoid scanning all documents.
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.
✗
The query is using 'array-contains' which always scans the entire collection.
Why it's wrong here
array-contains can use existing indexes if properly indexed.
✗
The 'status' field is not indexed because single-field indexes are not automatic.
Why it's wrong here
Single-field indexes are automatic in Native mode.
✗
The query is missing an ORDER BY clause causing a full scan.
Why it's wrong here
Missing ORDER BY does not cause a full scan if indexes are used.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that missing ORDER BY or using array-contains causes high reads, when in fact the real culprit is the lack of a composite index for inequality filters combined with equality filters.

Detailed technical explanation

How to think about this question

Firestore's query engine uses indexes to map sorted field values to document references. When an inequality filter is present on a field that is not part of a composite index with the equality filter field, the engine must scan all documents matching the equality condition and then evaluate the inequality filter in memory, which incurs read costs for every scanned document. Composite indexes allow Firestore to perform a single index scan that directly returns only the documents satisfying both conditions, drastically reducing reads. In real-world scenarios, this often catches developers off guard when they add a timestamp filter for date ranges without creating the corresponding composite index.

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.

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 PCDOE question test?

Manage Database Solutions — This question tests Manage Database Solutions — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The query is using an inequality filter on 'created_date' which requires a composite index. — In Firestore Native mode, queries that apply an inequality filter (e.g., >=, >, <, !=) on a field automatically require a composite index on both the equality filter field and the inequality filter field to avoid a full collection scan. Without that composite index, Firestore performs a back-end scan of all documents matching the equality filter, then applies the inequality filter in memory, resulting in high document reads. Option A correctly identifies that the inequality filter on 'created_date' is the most likely cause of the excessive reads because it forces Firestore to read and discard many documents that do not satisfy the timestamp condition.

What should I do if I get this PCDOE 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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Last reviewed: Jul 4, 2026

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This PCDOE practice question is part of Courseiva's free Google Cloud 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 PCDOE exam.