- A
Data Bundles
Why wrong: Data Bundles are for pre-packaged data, not access control.
- B
Security Rules
Correct: Security Rules allow condition-based access at the document level.
- C
Composite indexes
Why wrong: Indexes are for query performance, not security.
- D
IAM roles
Why wrong: IAM roles provide broad access, not document-level granularity.
Question 445 of 980
PCD Practice Question: Design Scalable and Highly Available Cloud Database Solutions
This PCD practice question tests your understanding of design scalable and highly available cloud 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.
Your mobile app uses Firestore to store user profiles. You need to restrict access so that users can only read/write their own data. Which Firestore feature should you use?
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
✓
Security Rules
Firestore Security Rules are the correct choice because they allow you to define granular access controls based on user identity. By using the `request.auth.uid` variable in your rules, you can restrict read and write operations to documents where the user's UID matches a field in the document (e.g., `resource.data.user_id == request.auth.uid`), ensuring users can only access their own data.
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.
- ✗
Data Bundles
Why it's wrong here
Data Bundles are for pre-packaged data, not access control.
- ✓
Security Rules
Why this is correct
Correct: Security Rules allow condition-based access at the document level.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Composite indexes
Why it's wrong here
Indexes are for query performance, not security.
- ✗
IAM roles
Why it's wrong here
IAM roles provide broad access, not document-level granularity.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between security controls (Security Rules) and performance optimizations (Composite indexes), so the trap here is confusing a feature that speeds up queries with one that enforces access restrictions.
Detailed technical explanation
How to think about this question
Firestore Security Rules are evaluated on the server side for every database operation, using a declarative syntax that supports conditions based on `request.auth`, `resource.data`, and `request.time`. Under the hood, rules are compiled into a boolean expression that must evaluate to `true` for the operation to proceed; a common subtlety is that rules do not filter data—they only allow or deny access, so a query that could return documents the user cannot read will fail entirely. In a real-world scenario, you might combine rules with Firestore indexes to ensure that queries are both secure and performant, e.g., by creating a composite index on `userId` and `timestamp` to allow users to list their own recent activity.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCD question test?
Design Scalable and Highly Available Cloud Database Solutions — This question tests Design Scalable and Highly Available Cloud Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Security Rules — Firestore Security Rules are the correct choice because they allow you to define granular access controls based on user identity. By using the `request.auth.uid` variable in your rules, you can restrict read and write operations to documents where the user's UID matches a field in the document (e.g., `resource.data.user_id == request.auth.uid`), ensuring users can only access their own data.
What should I do if I get this PCD 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 PCD 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 PCD exam.
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