Question 534 of 1,446
PCDE Automatic indexing Practice Question
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.)
⚠ Common exam trap
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.
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.
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.
- ✗
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This PCDE 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 PCDE exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.