Supported data types in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Firebase Firestore Supported Data Types

Which of the following data types is NOT supported by Firebase Firestore for storing in documents?

A GeoPoint

B Function

C Timestamp

D Array

💡 Hint

Think about what kinds of data Firestore can store directly in documents.

Firestore supports storing timestamps, geographic points, arrays, and many primitive types, but it does not support storing executable code like functions.

❓ service_behavior

intermediate

Behavior of Unsupported Data Types in Firestore

What happens if you try to store a JavaScript Date object directly in Firestore without converting it?

A It throws an error because Firestore requires a Timestamp type.

B It stores the Date object as a number representing milliseconds.

C It silently converts the Date to a Firestore Timestamp.

D It stores the Date object as a string automatically.

💡 Hint

Consider how Firestore expects date/time values to be formatted.

Firestore automatically converts JavaScript Date objects to its own Timestamp type when storing.

❓ Configuration

advanced

Storing Nested Data Structures in Firestore

Given the following Firestore document data, which option correctly represents a nested map with an array inside?

Firebase

const data = {
  user: {
    name: "Alice",
    roles: ["admin", "editor"]
  }
};

A {"user": {"name": "Alice", "roles": ["admin", "editor"]}}

B {"user": {"name": "Alice", "roles": "admin, editor"}}

C {"user": ["name", "Alice", "roles", ["admin", "editor"]]}

D {"user": {"name": "Alice", "roles": {"0": "admin", "1": "editor"}}}

💡 Hint

Think about how Firestore stores objects and arrays.

Firestore supports nested maps (objects) and arrays. Option A correctly uses a map with an array for roles.

❓ security

advanced

Security Implications of Storing Binary Data in Firestore

Which statement about storing binary data (like images) directly in Firestore is true?

A Firestore is optimized for large binary data and is the best place to store images.

B Binary data cannot be stored in Firestore at all.

C Firestore automatically compresses binary data to save space and cost.

D Storing large binary data in Firestore can increase costs and slow down reads.

💡 Hint

Consider Firestore's intended use and pricing model.

Firestore is designed for structured data, not large binary files. Storing large binaries increases cost and latency.

❓ Architecture

expert

Choosing Data Types for Efficient Firestore Queries

You want to store a user's status that can be one of: 'active', 'inactive', or 'pending'. Which data type choice allows the most efficient Firestore queries and indexing?

A Store status as a string field with values 'active', 'inactive', or 'pending'.

B Store status as a boolean field where true means active and false means inactive or pending.

C Store status as a number: 1 for active, 2 for inactive, 3 for pending.

D Store status as an array containing all possible statuses.

💡 Hint

Think about how Firestore indexes and queries string fields versus other types.

Storing status as a string allows clear, readable queries and efficient indexing. Boolean cannot represent three states. Numbers work but reduce readability. Arrays are not suitable for single status values.