10 Caching Interview Questions and Answers (2024)
Blog / 10 Caching Interview Questions and Answers (2024)
Caching is a fundamental concept in caching.
Caching is a technique in computing where frequently accessed data or computations are temporarily stored in a cache, a fast storage area.
Understanding the fundamentals of Caching and is a must know for most tech interviews.
This blog will get you up to speed with the most important Caching interview questions and help you nail your next interview.
What is caching?
Junior
- Caching is a technique in computing where frequently accessed data or computations are temporarily stored in a cache, a fast storage area. This process speeds up data retrieval, reduces the load on the original data source, and improves overall system efficiency.
- Caches can be memory-based, disk-based, or web-based, and they use policies like "Least Recently Used" (LRU) to manage stored data. While caching enhances performance, it also adds complexity, especially in maintaining data consistency and cache invalidation.
Name some common tools used for caching?
Junior
- Memcached: An in-memory caching system widely used for speeding up dynamic web applications by alleviating database load.
- Redis: An advanced key-value store known for its versatility. It's often used as a caching solution and supports data structures like strings, hashes, lists, and sets.
- Varnish: A web application accelerator, often used as a reverse proxy, specifically designed for caching HTTP requests to reduce the load on web servers.
- CDN (Content Delivery Network): Services like Cloudflare, Akamai, and AWS CloudFront cache content closer to users geographically to decrease load times for websites and online content.
- Browser Caching: Modern web browsers like Chrome, Firefox, and Safari use their own caching mechanisms to store web page resources locally to speed up reloads.
- Nginx: Often used as a reverse proxy and load balancer, Nginx also provides effective caching for web content.
What is a cache miss?
Junior
- A cache miss occurs when the data requested by a system is not found in the cache. This necessitates fetching the data from the slower, original data source, such as a hard drive or a remote server. Cache misses are significant in caching systems because they determine the effectiveness of the cache.
- A high rate of cache misses can indicate that the caching strategy is not optimally configured, leading to slower access times and reduced overall system performance. In contrast, a cache hit, where the data is found in the cache, results in faster data retrieval and improved efficiency.
What is cache invalidation?
Junior
- Cache invalidation is the process of removing or marking as outdated the data in a cache to prevent the use of stale or incorrect information. It's essential for maintaining data accuracy and consistency between the cache and the original data source.
- Key strategies include time-based invalidation, where data expires after a set period, and event-based invalidation, triggered by updates in the data source.
- Maintaining this balance is challenging but crucial for effective caching, ensuring users always receive the most current data without impacting system performance significantly.
Name some cache invalidation strategies.
Mid
- Time-Based Expiration (TTL): Automatically invalidates cache items after a set time interval.
- Change-Based Invalidation: Triggers invalidation in response to updates or deletions in the data store for high consistency.
- Least Recently Used (LRU): Invalidates items not accessed for the longest time.
- Write-Through Strategy: Updates the cache simultaneously with every data store update, ensuring immediate consistency.
- Manual Invalidation: Involves manually clearing cache entries, used in complex or specific scenarios.
- Versioning: Uses version numbers to invalidate outdated cached data when underlying data changes.
- Tag-Based Invalidation: Invalidates groups of cache entries based on shared tags, useful for bulk updates.
Don't Let One Question Ruin Your Interview...
Describe the impact of cache size on performance.
Mid
- Higher Hit Rate: Larger caches increase the likelihood of data being found in the cache, leading to faster access times.
- Reduced Primary Storage Load: More data in the cache means fewer accesses to slower primary storage, improving overall performance.
- Diminishing Returns: Increasing cache size beyond a certain point may not significantly improve performance, as frequently accessed data is often a small subset.
- Increased Resource Usage: Larger caches consume more memory or disk space, which can be a concern in resource-limited environments.
- Potentially Longer Search Time: In some systems, larger caches might lead to longer times to search within the cache.
- Cost Considerations: Larger caches, especially with faster storage technologies, can be more expensive.
- Overheads in Distributed Systems: In distributed caching, larger caches might increase the complexity and overhead of maintaining coherence and synchronization.
List the steps involved in implementing a basic cache system.
Mid
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
What are some common cache writing strategies?
Mid
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
What is cache replacement?
Senior
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
How would you handle cache synchronization in a distributed environment?
Senior
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Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit, sed quia non numquam eius modi tempora incidunt ut labore et dolore magnam aliquam quaerat voluptatem.