- A
Create a composite index for every query involving array fields.
Why wrong: Creating a composite index for every query is unnecessary; simple array-contains queries only need a single-field index, which is created automatically.
- B
Set index exemptions for arrays and maps to disable automatic indexing.
Why wrong: Setting index exemptions disables automatic indexing, which would prevent array-contains queries from working correctly.
- C
Use the 'array-contains' operator only on indexed arrays.
Correct. The array-contains operator can only be used on fields that are indexed. Since Firestore auto-indexes array fields, this is typically satisfied unless exemptions are set.
- D
Manually create indexes for each array field in the Firestore console.
Why wrong: Manually creating indexes for each array field is redundant because Firestore already auto-indexes them.
- E
Understand that array fields are automatically indexed as single-field indexes.
Correct. Knowing that array fields are automatically indexed as single-field indexes is key to understanding how array-contains queries work.
PCDOE Automatic indexing Practice Question
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. A key principle to apply: automatic indexing. 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 development team is using Firestore in Native mode. They want to ensure that queries on array fields return correct results. Which two actions should they take? (Choose TWO.)
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
Use the 'array-contains' operator only on indexed arrays.
Firestore automatically creates single-field indexes for all fields, including array fields. This means the array-contains operator works without manual indexing, provided the field has not been excluded via index exemptions. However, to ensure queries return correct results, developers must understand that array fields are indexed by default (E) and that array-contains only works on indexed arrays (C). Option B is incorrect because disabling indexing via exemptions would prevent array-contains queries from working.
Key principle: Automatic indexing
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 for every query involving array fields.
Why it's wrong here
Creating a composite index for every query is unnecessary; simple array-contains queries only need a single-field index, which is created automatically.
- ✗
Set index exemptions for arrays and maps to disable automatic indexing.
Why it's wrong here
Setting index exemptions disables automatic indexing, which would prevent array-contains queries from working correctly.
- ✓
Use the 'array-contains' operator only on indexed arrays.
Why this is correct
Correct. The array-contains operator can only be used on fields that are indexed. Since Firestore auto-indexes array fields, this is typically satisfied unless exemptions are set.
Related concept
Automatic indexing
- ✗
Manually create indexes for each array field in the Firestore console.
Why it's wrong here
Manually creating indexes for each array field is redundant because Firestore already auto-indexes them.
- ✓
Understand that array fields are automatically indexed as single-field indexes.
Why this is correct
Correct. Knowing that array fields are automatically indexed as single-field indexes is key to understanding how array-contains queries work.
Related concept
Automatic indexing
Common exam traps
Common exam trap: answer the scenario, not the keyword
A common trap is thinking that array fields require special manual indexing or that index exemptions are needed for queries to work. In reality, automatic indexing covers array fields, and exemptions only serve to exclude fields to reduce costs or meet specific requirements.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Automatic indexing
- array-contains operator
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
Automatic indexing
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. Automatic indexing 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.
Review automatic indexing, then practise related PCDOE questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this PCDOE question test?
Manage Database Solutions — This question tests Manage Database Solutions — Automatic indexing.
What is the correct answer to this question?
The correct answer is: Use the 'array-contains' operator only on indexed arrays. — Firestore automatically creates single-field indexes for all fields, including array fields. This means the array-contains operator works without manual indexing, provided the field has not been excluded via index exemptions. However, to ensure queries return correct results, developers must understand that array fields are indexed by default (E) and that array-contains only works on indexed arrays (C). Option B is incorrect because disabling indexing via exemptions would prevent array-contains queries from working.
What should I do if I get this PCDOE question wrong?
Review automatic indexing, then practise related PCDOE questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Automatic indexing
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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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