Revision - Client Data Caching Technique (Persistent Storage)

Question 1

What are the three primary benefits of implementing client data caching in a mobile app?

Answer 1

1. Offline Support : Enable to display data without internet connection
2. Performance : Loading data from local device is faster than network request
3. Cost Reduction : Prevents the app from constantly re-fetching same data from cloud database

Question 2

Which Flutter package should you use to store simple data types like the user’s theme preference (Light/Dark mode) or a simple authentication token?

Answer 2

shared_preferences

Question 3

Which Flutter package should you use to stores files (5MB PDF report) that the user wants to view later

Answer 3

path_provider

Save the PDF directly to the device Application Documents Directory

Question 4

Which Flutter package should you use to stores many data (List of expenses) that the user wants to view later?

Answer 4

sqflite

Data is highly structured and requires complex querying (Search expenses, filter expenses)

Question 5

What is the major limitation or security warning regarding shared_preferences?

Answer 5

1. It is not encrypted or secure by default
2. We should never store highly sensitive data without using specialized secure storage package (flutter_secure_storage)

Question 6

When reading/writing files using path_provider, what is the difference between the “Temporary Directory” and the “Application Documents Directory”?

Answer 6

1. Temporary Directory(Cache): The OS can delete files at any time if the device runs low on storage
2. Application Documents Directory: File stored here are permanent and will only be deleted if user unstalls the app

Question 7

In Flutter, reading or writing to local storage (SharedPreferences, SQLite, or Files) always returns what type of object? Why?

Answer 7

Future, because interacting with device’s hard drive takes time, it needs async and await to prevent blocking the UI

Question 8

If you see the code SharedPreferences.getInstance() followed by prefs.setBool(‘isDarkMode’, true), what caching technique is being used?

Answer 8

Key-Value Store (using shared_preferences package)