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50 Caching Interview Questions

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Fundamental Caching Questions

  1. What is caching and why is it used in software systems?
  2. Define a cache hit and a cache miss.
  3. What are the main purposes of using a cache?
  4. How does caching improve application performance?
  5. What is the difference between memory caching and disk caching?
  6. What types of data are best suited to be cached?
  7. What are the pros and cons of caching?
  8. What is locality of reference (temporal vs spatial)?
  9. When should you not use a cache?
  10. Describe where you might place caches in a typical web application stack.

Cache Operations & Mechanics

  1. What is a cache key and why is it important?
  2. Explain cache eviction (replacement) and why it’s necessary.
  3. Name common cache eviction strategies (LRU, LFU, FIFO).
  4. What is cache expiration and how is it handled?
  5. How does cache invalidation work?
  6. What are the trade-offs between cache size and performance?
  7. What is a cache stampede and how can you prevent it?
  8. How do you handle stale data in a cache?
  9. What is write-around, write-back, and write-through caching?
  10. Explain the differences in writing policies (write-through vs write-back).

Distributed Caching

  1. What is distributed caching?
  2. How is distributed cache different from local cache?
  3. What are the challenges of distributed caching?
  4. Explain cache partitioning (sharding).
  5. What is cache replication and why is it used?
  6. Discuss consistency models with distributed caches (eventual vs strong).
  7. How do you resolve cache coherence issues across nodes?
  8. How do you handle network latency in distributed caching?
  9. What is consistent hashing and how does it apply to caching?
  10. How do you handle cache failure or node loss in a distributed system?

Web & HTTP Caching

  1. What are HTTP cache headers (Cache-Control, ETag, Expires)?
  2. What is client-side caching vs server-side caching?
  3. How does CDN caching work and why is it important?
  4. How would you handle caching for REST APIs?
  5. Explain browser cache vs CDN cache differences.

Caching in Databases & Applications

  1. How does database query caching work?
  2. What is object caching and how is it used in backend services?
  3. How would you design a cache for search results or recommendations?
  4. In the context of Spring Boot (or Java), how do you enable caching?
  5. How would you measure and tune cache performance?

Scenario & Design Questions

  1. How would you design a distributed LRU cache service?
  2. How would you integrate caching into a system experiencing heavy read load?
  3. You have a cache with high stale reads — how do you improve freshness?
  4. Design a caching layer for social media feeds.
  5. What caching strategy would you use for a shopping cart service?

Performance, Metrics & Tradeoffs

  1. What metrics do you monitor for cache health (hit rate, eviction count)?
  2. How do you benchmark a caching solution?
  3. How does caching impact consistency and freshness of data?
  4. What trade-offs exist between read and write-heavy caches?
  5. How do you plan cache warm-up and invalidation in production?
Caching system design