Caching Strategies for Web Application Performance Quiz

Explore essential caching strategies in web applications with this quiz. Assess your understanding of common cache techniques, benefits, challenges, and best practices for optimizing web performance.

1. Understanding Browser Cache

   Which caching strategy stores web page assets like images and scripts directly on the user's device to speed up future visits?

   1. Edge cache
   2. Database cache
   3. Browser cache
   4. Server cache

   Explanation: Browser cache stores copied web assets locally on the user's device, allowing faster page loads on repeat visits. Edge cache stores content at network edges but not directly on the user's device. Database cache is used to speed up data retrieval from databases. Server cache refers to caching content on the web server rather than the end user’s device.

2. Function of Object Caching

   What is the main advantage of object caching in a web application backend?

   1. Increases browser storage usage
   2. Slows down database queries
   3. Reduces time needed to recompute expensive operations
   4. Deletes cached static content

   Explanation: Object caching saves the result of resource-intensive or frequent operations, reducing the need to repeat them and thus improving efficiency. It does not increase browser storage usage, as that is handled by browser cache. It actually speeds up (not slows down) database queries by storing results in memory. It does not delete static content; instead, it stores objects temporarily.

3. Pros of CDN Caching

   When using a CDN cache, what is the primary benefit for users located far from the origin server?

   1. Higher likelihood of displaying outdated data
   2. Manual request for every server update
   3. Increased memory usage on mobile devices
   4. Faster content delivery due to reduced distance

   Explanation: CDN caches serve content from distributed locations closer to users, minimizing delays and speeding up delivery. They do not affect mobile device memory directly. Users do not manually request every update; the CDN updates content as configured. While caching can potentially serve stale data, proper configuration minimizes this risk, and the primary advantage is still faster delivery.

4. Cache Invalidation Basics

   Which term refers to the process of removing or updating outdated cached content so users receive the most recent data?

   1. Cache transformation
   2. Cache fragmentation
   3. Cache invalidation
   4. Cache miss

   Explanation: Cache invalidation ensures old or stale data is replaced with updated content, so users access the latest information. Cache fragmentation is not a related concept in web caching. Cache transformation is not a standard term. A cache miss occurs when requested data is not found in cache, not when updating stale content.

5. Understanding Cache-Control Header

   What does the 'Cache-Control: no-store' HTTP header instruct browsers and caches to do?

   1. Store the response for 10 seconds
   2. Share the response with all users
   3. Double the cache expiration time
   4. Never store the response in any cache

   Explanation: The 'no-store' directive tells browsers and all caches not to save the response under any circumstances, improving privacy and dynamic content safety. Storing the response for 10 seconds or doubling cache time would use different directives. Sharing with all users is unrelated to the 'no-store' directive.

6. Benefits of Cache Revalidation

   Why is cache revalidation useful when serving web content that changes infrequently?

   1. It disables caching for all users
   2. It increases the memory required to cache files
   3. It only speeds up database queries
   4. It ensures users see updated content while still benefiting from caching

   Explanation: Cache revalidation checks if content has changed before serving cached data, combining freshness with performance improvements. It does not disable caching—rather, it makes caching more reliable. Speeding up database queries is the role of database or object caching. Increasing memory use is not an intended advantage of revalidation.

7. Cache Miss Scenario

   What happens during a cache miss when a user requests a web page?

   1. The content is fetched from the original source and then cached
   2. The cache immediately returns outdated data
   3. The server deletes all cache entries
   4. The request is refused by the cache

   Explanation: During a cache miss, the cache does not contain the requested data, so it must retrieve it from the original source and typically stores it for future use. Returning outdated data would be a cache hit with stale data, not a miss. Servers do not delete all cache entries because of a cache miss, nor do caches refuse legitimate requests.

8. Distinguishing Write-Through Cache

   Which statement describes a write-through cache in a web application context?

   1. Data is only read from the cache and never updated
   2. Data is only written to the cache and updated in the database later
   3. Cache ignores any write operations
   4. Data is written to both the cache and the underlying data store simultaneously

   Explanation: A write-through cache ensures every data write goes to both the cache and the data store at the same time, keeping both in sync. Writing only to the cache and updating the database later is called write-back or write-behind caching. Ignoring writes or only reading from the cache are incorrect because caches need to stay updated.

9. Eviction Policy Purpose

   Why do caching systems use an eviction policy such as Least Recently Used (LRU)?

   1. To fetch only the most popular web pages
   2. To increase the cache memory size automatically
   3. To encrypt all cached data
   4. To remove old or less accessed items when cache space is limited

   Explanation: Eviction policies like LRU help caches manage limited space by removing data that hasn't been used recently, making room for new data. They do not increase the cache size, only make better use of it. Fetching popular pages and encryption are not the purposes of eviction policies, although they may play roles elsewhere.

10. Drawback of Caching Dynamic Data

    What is a potential drawback of caching highly dynamic web content, such as live sports scores?

    1. The cache saves too much memory on the server
    2. Users may see outdated or incorrect information
    3. It improves security but slows performance
    4. The cache only works for static assets

    Explanation: Caching very dynamic content can result in users receiving stale data instead of real-time updates, which may lead to displaying incorrect information. Caching uses memory but does not automatically save excessive amounts beyond configured limits. Caching does not inherently improve security or only serve static assets; it is configurable for various content types.