Manage a solution that can span multiple database technologies →mediumMultiple ChoiceObjective-mapped
PCDE Practice Question: Manage a solution that can span multiple database technologies
A company uses Firestore in Native mode for their application. They need to query a collection where documents must match a specific field value and be sorted by a different field. The query filters on 'status' and orders by 'timestamp'. What should the engineer do to ensure the query performs optimally?
⚠ Common exam trap
Google exams often test the misconception that automatic single-field indexes are sufficient for all queries, but the trap here is that queries combining an equality filter and an order by on different fields always require a composite index.
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 'status' and 'timestamp' fields.
Firestore requires a composite index when a query includes both an equality filter on one field (status) and an order by clause on a different field (timestamp). Without this composite index, Firestore cannot efficiently satisfy both the filter and the sort order in a single index scan, leading to suboptimal performance or query failure. Creating a composite index on (status, timestamp) allows Firestore to use a single index to match the filter and return results in the requested order.
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 an index exemption to improve query performance.
Why it's wrong here
Index exemptions are used to exclude indexes on arrays and maps, not to improve performance.
- ✗
Use a collection group query to bypass index requirements.
Why it's wrong here
Collection group queries also need indexes; they do not bypass index requirements.
- ✗
Rely on automatic single-field indexes; they will cover the query.
Why it's wrong here
Single-field indexes are not sufficient for combined filter and order queries.
- ✓
Create a composite index on the 'status' and 'timestamp' fields.
Why this is correct
A composite index is required for queries with both an equality filter and an order by on different fields.
Go deeper
Related to this question
About these practice questions
This PCDE question is part of Courseiva's 1,446-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.