Assess your understanding of Firestore's key features, data structure, security rules, and best practices for cloud storage in mobile app development. This quiz covers essential concepts to help you confidently use Firestore for scalable and real-time mobile applications.
Which element is the top-level organizational unit for storing data in Firestore, where collections hold documents?
Explanation: A collection is the main organizational unit in Firestore and contains documents that store data. Fields are key-value pairs within documents, while arrays are a data type used within fields, not organizational units. References are used to point to specific documents but do not organize data at the top level.
If a user profile document includes fields for name, email, and age, what data format is used to store these fields in Firestore?
Explanation: Firestore stores document data as key-value pairs, allowing flexible and dynamic field definitions. Plain text would not support complex data access, single arrays would be insufficient for complex structures, and table rows are not the storage model used in Firestore.
In Firestore, how can a mobile app receive immediate updates when a document changes, such as displaying a chat message instantly?
Explanation: Listeners can be attached to documents or collections in Firestore, enabling real-time updates in the app. Timers and polling involve repeatedly checking for changes, which is less efficient and slower. Archives are unrelated to receiving live updates.
Which of the following is NOT allowed when querying a collection in Firestore?
Explanation: Firestore supports queries with single field inequalities and ordering or limiting the result set. However, using multiple inequality conditions on different fields in a single query is not permitted and will result in an error. The other options are all supported query operations.
What feature allows mobile apps to access and modify Firestore data even when there is no internet connection?
Explanation: Offline persistence enables apps to read and write Firestore data offline by storing a local cache and syncing changes once connectivity is restored. Hard refresh and cache clearing remove cached data, which would not support offline capabilities, and data shuffling is unrelated to offline access.
How do security rules in Firestore control access to data by mobile users?
Explanation: Security rules examine each read or write request and allow or deny it based on specified conditions, such as authentication or data values. Changing document fields is a data operation, not an access control method. Deleting collections and updating client libraries do not involve access control.
When designing a Firestore database for a mobile app with users and posts, which structure is recommended for efficiency?
Explanation: Having separate collections for users and posts provides scalability and efficient queries. Placing all data into a single document or array limits performance and flexibility, while a collection containing only images would not address all app data requirements.
Which of the following is a supported data type for Firestore document fields?
Explanation: Timestamps are natively supported in Firestore and are useful for storing dates and times. Bitmaps and text tables are not direct data types, and CSV row is not a recognized Firestore type; CSV data would need to be stored as plain text or parsed.
What helps Firestore to handle large-scale mobile applications with quick queries and concurrent users?
Explanation: Firestore automatically indexes documents for fast queries and high scalability, which is crucial for large-scale apps. Manual sharding is rarely needed and could add complexity, sequential writes limit concurrency, and data encryption, while important, does not address query speed or scalability.
Which Firestore method should be used to atomically update multiple documents, such as deducting stock from different products in a mobile store app?
Explanation: Batch write allows multiple writes to execute atomically, so all succeed or all fail together. Single insert only affects one document, array merge is for merging array fields, and batched response is not an actual method in Firestore.