Câu hỏi phỏng vấn [Global] Caching
Câu hỏi

What is Cache Invalidation?

Câu trả lời

Cache invalidation is the process of removing or updating outdated data from a cache to ensure that only the most recent and accurate data is stored. This is crucial for maintaining data consistency and accuracy, especially in scenarios where the source data can change frequently. Without cache invalidation, applications might serve stale or incorrect data, leading to potential errors and inconsistencies.

Reasons for Cache Invalidation

  1. Data Freshness: Ensures that the cached data reflects the most recent changes in the source data.
  2. Resource Optimization: Prevents the caching of unnecessary or outdated data, optimizing cache resource utilization.
  3. Data Consistency: Guarantees that data across different components or modules remains consistent, particularly in multi-tier or distributed systems.

Common Cache Invalidation Techniques

  1. Time-Based Invalidation: Cached data is considered valid for a specific duration, after which it is discarded as potentially outdated. This technique is also known as "time-to-live" (TTL) expiration[2][4].
  2. Event-Based Invalidation: The cache is updated when specific events occur in the data source, ensuring data accuracy. This is often implemented in "write-through" caches[4].
  3. Key-Based Invalidation: Caching mechanisms are designed around specific keys or identifiers. When relevant data changes in the source, the corresponding key is marked as invalid or removed from the cache[4].
  4. Hybrid Invalidation: Combines multiple techniques to tailor the approach to specific data or use cases for more precise cache management[4].

Challenges in Cache Invalidation

  1. Complexity of Dependencies: Determining which content needs to be invalidated based on multiple dependencies can be complex[6].
  2. Timing: Determining the right time to invalidate the cache is crucial to avoid serving outdated content or causing delays in seeing updated content[6].
  3. Granularity: Ensuring that only the relevant content is invalidated requires careful management of cache keys and expiration times[6].
  4. Consistency: Maintaining consistency across distributed caches can be challenging...
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