The correct answer is that all authenticated users can read all documents. This is a critical security concern because the Firestore security rules use a broad wildcard pattern—`match /databases/{database}/documents`—combined with a read permission that only checks for authentication status via `request.auth != null`, without any document-level or collection-level restrictions. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of the principle of least privilege and how overly permissive rules can lead to unauthorized data exposure. A common trap is assuming that authentication alone is sufficient for access control, but the exam emphasizes that you must scope rules to specific collections or documents and enforce data ownership or role-based checks. Remember the memory tip: “Auth is not enough—scope your stuff.”
PCDE Plan and manage database infrastructure Practice Question
This PCDE practice question tests your understanding of plan and manage database infrastructure. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Exhibit
service cloud.firestore {
match /databases/{database}/documents {
match /{document=**} {
allow read: if request.auth != null;
allow write: if request.auth != null && request.auth.uid == resource.data.owner;
}
}
}
Refer to the exhibit. A developer deployed these Firestore security rules. What is a security concern with this configuration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
All authenticated users can read all documents
Option C is correct because the Firestore security rules shown grant read access to all authenticated users without any document-level or collection-level restrictions. The rule `match /databases/{database}/documents { allow read: if request.auth != null; }` applies to all documents in the database, meaning any authenticated user can read every document, including those they should not have access to. This violates the principle of least privilege and can lead to unauthorized data exposure.
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.
✗
Only the owner can write to documents
Why it's wrong here
This is a good security practice, not a concern.
✗
The rules do not explicitly allow delete operations
Why it's wrong here
If not allowed, delete is implicitly denied by Firestore; this is correct.
✓
All authenticated users can read all documents
Why this is correct
The read rule allows any authenticated user to read any document, which may leak private data.
Related concept
Read the scenario before looking for a memorised answer.
✗
The wildcard path matches all databases
Why it's wrong here
The pattern {database} is a variable that matches a single database, not a security issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that 'authenticated users' implies safe access, but the trap here is that without document-level conditions, all authenticated users can read every document, which is a common misconfiguration in Firestore security rules.
Detailed technical explanation
How to think about this question
Firestore security rules use a hierarchical matching system where `match /databases/{database}/documents` applies to all collections and documents under the default or any named database. The `allow read` and `allow write` statements are evaluated per request; if not explicitly separated (e.g., `allow create, update, delete`), a single `allow write` grants all mutation operations. In production, rules should use granular conditions like `resource.data.owner == request.auth.uid` to enforce document-level access control, preventing authenticated users from reading or writing data they do not own.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: All authenticated users can read all documents — Option C is correct because the Firestore security rules shown grant read access to all authenticated users without any document-level or collection-level restrictions. The rule `match /databases/{database}/documents { allow read: if request.auth != null; }` applies to all documents in the database, meaning any authenticated user can read every document, including those they should not have access to. This violates the principle of least privilege and can lead to unauthorized data exposure.
What should I do if I get this PCDE 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.
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Question Discussion
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