- A
Create a composite index on the three fields
Composite indexes must be created manually for queries that filter on multiple fields and order by another.
- B
Rely on automatic single-field indexes
Why wrong: Automatic single-field indexes cannot support queries that filter on multiple fields or order by a different field.
- C
Use an index exemption on the fields
Why wrong: Index exemptions are used to exclude arrays and maps from automatic indexing, not for composite indexes.
- D
Use Firestore in Datastore mode instead
Why wrong: Datastore mode also requires composite indexes for multi-field queries; switching mode does not help.
Question 944 of 1,000
PCDOE Manage Database Solutions Practice Question
This PCDOE practice question tests your understanding of manage database solutions. 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.
An e-commerce application uses Firestore in Native mode. The team needs to run a query that filters on two fields and orders by a third field. What is the correct approach to ensure this query runs efficiently?
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
✓
Create a composite index on the three fields
Firestore requires a composite index for queries that filter on multiple fields and order by a different field, because single-field indexes cannot satisfy the combined filtering and ordering constraints. Creating a composite index on the three fields (the two filter fields and the order field) allows Firestore to efficiently execute the query without scanning all documents.
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 composite index on the three fields
Why this is correct
Composite indexes must be created manually for queries that filter on multiple fields and order by another.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Rely on automatic single-field indexes
Why it's wrong here
Automatic single-field indexes cannot support queries that filter on multiple fields or order by a different field.
- ✗
Use an index exemption on the fields
Why it's wrong here
Index exemptions are used to exclude arrays and maps from automatic indexing, not for composite indexes.
- ✗
Use Firestore in Datastore mode instead
Why it's wrong here
Datastore mode also requires composite indexes for multi-field queries; switching mode does not help.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that single-field indexes are sufficient for multi-field queries, or that index exemptions can be used to optimize queries, when in fact composite indexes are mandatory for such queries in Firestore.
Detailed technical explanation
How to think about this question
Under the hood, Firestore uses a B-tree-like index structure for composite indexes, where the index order is defined by the fields in the index definition. The query planner uses the composite index to merge the filter conditions and the ordering in a single index scan, avoiding a sort operation. A real-world scenario is an e-commerce app querying for products where 'category = electronics' and 'price > 50' ordered by 'rating'—without a composite index on (category, price, rating), Firestore would either fail or perform a full collection scan.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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.
- →
Manage Database Solutions — study guide chapter
Learn the concepts, then practise the questions
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Manage Database Solutions practice questions
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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: Create a composite index on the three fields — Firestore requires a composite index for queries that filter on multiple fields and order by a different field, because single-field indexes cannot satisfy the combined filtering and ordering constraints. Creating a composite index on the three fields (the two filter fields and the order field) allows Firestore to efficiently execute the query without scanning all documents.
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.
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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Last reviewed: Jul 4, 2026
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.
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