Definition
Cache invalidation is a computer process that renders cached data invalid. This removes the content and will no longer be displayed upon request. The aim is to serve the user with the newest content version when they request.
Cache invalidation can also help optimize websites, reduce loading time, and use fewer servers. It can be performed independently or included in the coherence protocol.
Cache invalidation Methods
- Purging: Removes invalidated and cached content from the caching proxy instantly.
- Refreshing: Cached content is fetched from an application even if it is available in the cache. Also, the cached content is replaced with the most recent version of the application. However, this refreshment only impacts only one version of the cached content.
- Banning: Involves referencing the cached content to a blocklist. So, the user request is checked against the blocklist, and if it matches, the user is served with the newest content from the application, which is added to the cache.
How Does Cache Invalidation Work?
Website caching can lead to outdated information if the cache isn’t refreshed. Cache invalidation ensures cache reflects the latest data from the server. Invalidation involves syncing data across system layers, which requires careful coordination. If a change is made on one layer, it should be propagated to other layers to maintain system consistency.
An invalid result appears in the cache if one input changes. Moreover, the software may continue working, making it difficult to identify the problem to solve the cache invalidation logic.
Generally, a cache retains frequently accessed data, making it easy and quicker to retrieve it and reducing the strain on the original storage. Usually, applications check the cache first for data; if not found, they fetch it from primary storage. The newly obtained data is stored in the cache for faster retrieval in the future.
Various factors can influence cache invalidation. For example, cookies can be used to manage cache invalidation by linking specific cache entries with user-specific data.
Benefits of Cache Invalidation
- Improved performance: The process removes outdated data, thereby improving cache retrieval rate and overall device performance.
- Improved system scalability: Removing unwanted data from servers improves system’s performance and scalability.
- Lower costs: Cache invalidation reduces the need for additional resources required for system operations thus reducing systemic costs.
- Improved security: Clearing up unwanted data minimizes the risk of data theft.
- Enhanced user experience: It reduces latency and guarantees a better user experience due to faster load times.
- Compliance with laws: Cache invalidation helps meet regulatory requirements such as CCPA, GDPR and HIPAA.
Strategies for Cache Invalidation
- Least recently used (LRU): When the memory is full, the system removes the cache that hasn’t been used recently to make space for new cache. It assumes least recently used content won’t be needed in future.
- Least frequently used (LFU): The algorithm clears up the cache that is used the fewest times when the cache capacity is reached.
- Random replacement: When the cache is full, the system randomly picks cache to be removed, assuming that each cache has an equal chance of being used in the future.
- First In, First Out (FIFO): The algorithm gets rid of the oldest cache first to make space for new ones.