Caching Strategies for Mobile Data: Concepts and Best Practices Quiz

This quiz challenges your understanding of advanced caching mechanisms on mobile platforms, exploring client/server approaches, TTL management, cache keys, ETags, bandwidth strategies, and offline data handling.

1. Client vs. Server Caching Responsibilities

   Which of the following best describes the main responsibility of server-side caching in mobile applications compared to client-side caching?

   1. Server-side caching is used only for permanent storage, while client-side caching controls temporary storage.
   2. Server-side caching manages user authentication, while client-side caching stores user credentials.
   3. Server-side caching invalidates all cached entries automatically, while client-side caching never expires.
   4. Server-side caching updates user interfaces instantly, while client-side caching controls push notifications.
   5. Server-side caching reduces repeated data processing and conserves backend resources, while client-side caching primarily minimizes repeated network requests for the same data.

2. Purpose of TTL in Caching

   In a scenario where news articles are cached on a user's device for offline access, what is the primary function of setting a TTL (Time-To-Live) value for each cached article?

   1. It encrypts articles for the duration of their storage.
   2. It determines the number of devices allowed to access the cached article.
   3. It limits the bandwidth used when synchronizing cached articles.
   4. It specifies how long each article remains valid before it is considered stale and needs to be refreshed.
   5. It prevents cached articles from being read offline.

3. Cache Key Construction

   When caching API responses for a weather app that includes different locations and date ranges, which statement best explains the importance of constructing effective cache keys?

   1. The cache key should be a constant string to reduce complexity.
   2. Cache keys only need to reflect the time of the last access.
   3. Using user passwords as cache keys ensures security.
   4. Cache keys are irrelevant if ETags are always used.
   5. A well-constructed cache key uniquely identifies each response by including parameters such as location and date, avoiding cache collisions and incorrect data retrieval.

4. ETags in Bandwidth Optimization

   Given a situation where a mobile app uses ETags with resource requests, how does this mechanism help minimize unnecessary bandwidth consumption?

   1. The server compresses all responses when ETags are used.
   2. ETags increase the cache size, reducing bandwidth for large files.
   3. ETags encrypt the data in transit, reducing its size.
   4. The client sends its cached ETag with the request, and if the server's resource hasn't changed, only a small 'Not Modified' response is returned instead of the full content.
   5. ETags automatically renew the TTL on all cached items.

5. Offline Data Access Strategies

   Which technique is best used to ensure access to user playlists in a music streaming app when the device is temporarily offline?

   1. Sync playlists only at device startup regardless of network changes.
   2. Encrypt playlists instead of caching them for offline access.
   3. Disable caching entirely and fetch playlists only on demand.
   4. Cache relevant playlists locally when online and set appropriate TTLs to check periodically for updates upon reconnecting.
   5. Purge all cached playlists whenever the app is closed.

6. Cache Invalidation Challenge

   If a mobile photo-sharing app caches a user's photo gallery, what is a potential issue if cache invalidation is not handled properly when photos are deleted on another device?

   1. Invalidation causes the app to crash upon gallery reload.
   2. Photo metadata will be permanently lost on the server.
   3. The app will automatically remove all user accounts.
   4. Deleted photos might still appear in the cached gallery until the cache is invalidated or refreshed.
   5. Caching will stop working for all future photo uploads.

7. Advanced Caching: Stale-While-Revalidate

   In the 'stale-while-revalidate' caching pattern, how is fresh content served to users in a mobile shopping app immediately after they open the app from offline mode?

   1. The cached data is encrypted and unreadable until refreshed.
   2. The app first serves potentially stale cached content instantly, then fetches updated data in the background and refreshes the cache.
   3. The cache is discarded and only live content is used.
   4. The app waits for fresh content to arrive before displaying anything.
   5. Stale-while-revalidate disables caching for popular products.

8. Hashing and Collisions in Cache Keys

   What is a potential risk of generating cache keys for API responses by simply hashing request URLs without including all query parameters in the input?

   1. The hash makes caching completely insecure.
   2. Requests with different parameter values could generate the same hash, causing incorrect cached responses (cache collisions).
   3. The performance of the device cache improves drastically.
   4. All new requests bypass the cache entirely.
   5. The cache expunges entries too quickly due to hash length.

9. Priority Caching for Bandwidth Management

   Consider a mobile app with access to limited bandwidth and storage; what is an effective strategy for prioritizing what to cache?

   1. Never cache user-facing data and only cache system logs.
   2. Use random selection to determine which items to cache.
   3. Cache only the largest files to maximize storage use.
   4. Cache high-priority or frequently accessed data, such as user profiles or messages, while omitting rarely used content to optimize for performance and bandwidth.
   5. Cache all files with equal priority regardless of size.

10. Handling Cache Consistency During Network Fluctuations

    When a user's device moves frequently between online and offline states, which approach helps ensure consistent data when using client-side caching?

    1. Implement conflict resolution logic to merge cached changes with server data upon reconnection, reducing the risk of overwriting or losing updates.
    2. Refresh the cache only after device reboot.
    3. Rely solely on TTL expiration to maintain consistency.
    4. Let users manually choose which cache entries to sync.
    5. Disable all caching whenever the network is unstable.