Multi-tenancy patterns in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Multi-tenancy Isolation Levels

In Firebase multi-tenancy, which isolation level best ensures that data from one tenant cannot be accessed by another tenant?

A Shared database with tenant ID filtering in queries

B Single Firestore collection with tenant data mixed

C Shared Firebase project with different Firestore collections per tenant

D Separate Firebase projects for each tenant

💡 Hint

Think about physical separation of data and access control.

Using separate Firebase projects for each tenant provides the strongest isolation because each tenant's data and resources are completely separated at the project level.

❓ Architecture

intermediate

Choosing a Multi-tenancy Data Model in Firestore

You want to design a Firestore database for multiple tenants. Which data model allows easy querying of tenant-specific data while minimizing data duplication?

A One collection per tenant with duplicated structure

B Single collection with tenant ID field in each document

C Separate Firestore projects per tenant

D Single collection with tenant data mixed without tenant ID

💡 Hint

Consider how queries filter data efficiently.

A single collection with a tenant ID field allows filtering by tenant while keeping the structure consistent and avoiding duplication.

❓ security

advanced

Securing Tenant Data with Firebase Security Rules

Given a Firestore collection 'orders' where each document has a 'tenantId' field, which Firebase security rule correctly restricts read access to documents belonging only to the authenticated tenant?

match /orders/{orderId} {
  allow read: if ... ;
}

A request.auth.token.tenantId == resource.data.tenantId

B request.auth.uid == resource.data.tenantId

C resource.data.tenantId == 'tenant123'

D request.auth.token.email == resource.data.tenantId

💡 Hint

Check how tenant identity is passed in the authentication token.

The tenant ID should be included in the user's auth token and matched against the document's tenantId field to enforce access control.

❓ service_behavior

advanced

Behavior of Firebase Functions in Multi-tenant Setup

In a multi-tenant Firebase app using a single project, what happens if a Cloud Function does not check tenant identity before processing a request?

A Function runs only for the first tenant that called it

B Function automatically restricts access to the calling tenant's data

C Function processes requests for all tenants without restriction

D Function throws an authentication error

💡 Hint

Consider default behavior without explicit tenant checks.

Without explicit tenant checks, the function will process all requests regardless of tenant, risking data leaks.

✅ Best Practice

expert

Optimizing Cost and Performance in Firebase Multi-tenancy

You manage a Firebase app serving multiple tenants with varying usage patterns. Which multi-tenancy pattern best balances cost efficiency and performance?

A Single Firebase project with tenant ID filtering and Firestore rules

B Separate Firebase projects per tenant regardless of size

C Single Firebase project with duplicated collections per tenant

D Shared Firebase project with no tenant separation

💡 Hint

Think about managing resources and scaling efficiently.

A single Firebase project with tenant ID filtering and security rules allows sharing resources while isolating data logically, optimizing cost and performance.