Multi-tenancy patterns in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize Firebase for a specific tenant.

Firebase

const app = initializeApp({ projectId: [1] });

Drag options to blanks, or click blank then click option'

A'shared_project'

B'tenant_project_123'

C'default_project'

D'global_project'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a shared or global project ID which mixes tenant data.

Using the default project which is not tenant-specific.

Each tenant should have its own project ID to isolate resources.

2fill in blank

medium

Complete the code to set Firestore rules for tenant data isolation.

Firebase

match /databases/{database}/documents {
  match /users/{userId} {
    allow read, write: if request.auth.token.[1] == userId;
  }
}

Drag options to blanks, or click blank then click option'

Aemail

BtenantId

Crole

Duid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'tenantId' which is not a standard auth token property.

Using 'email' which is not a secure identifier for rules.

The 'uid' in the auth token matches the user ID to ensure users access only their data.

3fill in blank

hard

Fix the error in the Firestore query to fetch tenant-specific data.

Firebase

const query = firestore.collection('orders').where('tenantId', '==', [1]);

Drag options to blanks, or click blank then click option'

A'tenantId'

Btenant_id

CtenantId

Dtenant

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the field name inside the where method parameter.

Using incorrect field names like 'tenant_id' or 'tenant'.

The field name in the database is 'tenantId' without quotes in the query method.

4fill in blank

hard

Fill both blanks to create a Firestore document path for tenant data isolation.

Firebase

const docRef = firestore.collection([1]).doc([2]);

Drag options to blanks, or click blank then click option'

A'tenants'

B'tenantId'

C'users'

D'userId'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing collection and document names incorrectly.

Using 'tenantId' as a document ID instead of 'userId'.

The collection is 'tenants' and the document is the specific 'userId' to isolate tenant data.

5fill in blank

hard

Fill all three blanks to define a Firestore security rule for multi-tenant data access.

Firebase

match /[1]/{docId} {
  allow read, write: if request.auth.token.[2] == resource.data.[3];
}

Drag options to blanks, or click blank then click option'

Atenants

BtenantId

Dusers

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'users' instead of 'tenants' in the match path.

Mismatching token and data field names.

The rule matches the 'tenants' collection and checks that the auth token's 'tenantId' matches the document's 'tenantId' field.

Practice

1. What is the main purpose of multi-tenancy in Firebase applications?

easy

A. To allow multiple users to share the same app while keeping their data separate

B. To increase the speed of database queries

C. To reduce the cost of Firebase hosting

D. To enable offline data access for users

Solution

1. Step 1: Understand multi-tenancy concept

   Multi-tenancy means many users use one app but their data stays separate.

2. Step 2: Identify the purpose in Firebase context

   Firebase apps use multi-tenancy to keep user data isolated while sharing the app.

3. Final Answer:

   To allow multiple users to share the same app while keeping their data separate -> Option A

4. Quick Check:

   Multi-tenancy = separate data for shared app [OK]

Hint: Multi-tenancy means shared app, separate data [OK]

Common Mistakes:

• Confusing multi-tenancy with performance optimization
• Thinking multi-tenancy is about offline access
• Assuming multi-tenancy reduces hosting costs

2. Which Firestore data structure is best for separating tenant data in a multi-tenant Firebase app?

easy

A. A single collection with tenant ID as a field in each document

B. Separate collections for each tenant grouped by tenant ID

C. One document per tenant with all data nested inside

D. Storing all tenant data in one document without tenant ID

Solution

1. Step 1: Review Firestore data organization

   Firestore uses collections and documents to organize data.

2. Step 2: Choose best pattern for tenant separation

   Grouping data by tenant ID in separate collections keeps tenant data isolated and easier to secure.

3. Final Answer:

   Separate collections for each tenant grouped by tenant ID -> Option B

4. Quick Check:

   Tenant data separated by collections = Separate collections for each tenant grouped by tenant ID [OK]

Hint: Use collections grouped by tenant ID for clear separation [OK]

Common Mistakes:

• Putting all tenant data in one document
• Not using tenant ID to separate data
• Using a single collection without grouping

3. Given this Firestore security rule snippet for multi-tenancy:

match /tenants/{tenantId}/data/{docId} {
  allow read, write: if request.auth.token.tenant == tenantId;
}

What happens if a user with tenant ID 'tenantA' tries to read data from 'tenantB'?

medium

A. Access is granted because tenant IDs are ignored

B. Access is granted only for read but not write

C. Access is denied only if the document does not exist

D. Access is denied because tenant IDs do not match

Solution

1. Step 1: Understand the security rule condition

   The rule allows access only if the user's tenant ID matches the tenantId in the path.

2. Step 2: Apply the condition to the user and requested tenant

   User's tenant ID is 'tenantA' but tries to access 'tenantB' data, so condition fails.

3. Final Answer:

   Access is denied because tenant IDs do not match -> Option D

4. Quick Check:

   Tenant ID mismatch blocks access [OK]

Hint: Tenant ID in token must match path tenant ID [OK]

Common Mistakes:

• Assuming access is granted without tenant ID check
• Thinking read access is allowed but write is denied
• Ignoring tenant ID in security rules

4. You wrote this Firestore rule for multi-tenancy:

match /tenants/{tenantId}/data/{docId} {
  allow read, write: if request.auth.token.tenantId == tenantId;
}

But users report access errors. What is the likely problem?

medium

A. The token field name is incorrect; it should be 'tenant' not 'tenantId'

B. The path variable 'tenantId' is not defined in the rule

C. Firestore does not support tenant-based security rules

D. The rule allows access to all tenants without restriction

Solution

1. Step 1: Check token field name in the rule

   The rule uses 'request.auth.token.tenantId' but the token field is usually 'tenant'.

2. Step 2: Understand impact of wrong token field

   If the token field name is wrong, the condition always fails, causing access errors.

3. Final Answer:

   The token field name is incorrect; it should be 'tenant' not 'tenantId' -> Option A

4. Quick Check:

   Correct token field name fixes access [OK]

Hint: Match token field name exactly in rules [OK]

Common Mistakes:

• Using wrong token field name
• Assuming Firestore ignores token field names
• Not defining path variables correctly

5. You want to design a Firebase app supporting multiple tenants with isolated data and secure access. Which combination of patterns is best?

hard

A. Use a single Firestore collection for all tenants and filter data in the app code

B. Use Firebase Realtime Database instead of Firestore for multi-tenancy

C. Create separate Firestore collections per tenant and enforce tenant ID checks in security rules

D. Store all tenant data in one document and use client-side filtering for access control

Solution

1. Step 1: Evaluate data separation methods

   Separate collections per tenant keep data isolated and easier to manage.

2. Step 2: Apply security best practices

   Security rules must check tenant ID to prevent unauthorized access.

3. Step 3: Compare options

   Create separate Firestore collections per tenant and enforce tenant ID checks in security rules combines data separation and security rules, ensuring isolation and protection.

4. Final Answer:

   Create separate Firestore collections per tenant and enforce tenant ID checks in security rules -> Option C

5. Quick Check:

   Separate collections + security rules = best multi-tenancy [OK]

Hint: Combine data separation with security rules for best isolation [OK]

Common Mistakes:

• Relying on client-side filtering only
• Using single collection without security rules
• Choosing Realtime Database without need