Cache invalidation is a crucial process in computer systems to ensure that cached data remains consistent and up-to-date. Here are some common cache invalidation methods:
1. Purge
Description: This method removes the content from the cache immediately. When the client requests the data again, it is fetched from the application and stored in the cache.
Use Case: Suitable for scenarios where immediate removal of all variants of cached content is necessary.
Example: An e-commerce site updates product prices and needs the changes to reflect immediately[2][6].
2. Refresh
Description: This method fetches the requested content from the application, even if cached content is available. The existing cached content is replaced with the new version.
Use Case: Useful when only one variant of the cached content needs to be updated.
Example: A news website updates an article and wants the latest version to be served to users[2][6].
3. Ban
Description: Adds a reference to the cached content to a blacklist. Client requests are checked against this blacklist, and if a match is found, new content is fetched from the application and cached.
Use Case: Effective for invalidating content based on specific criteria without immediate removal.
Example: A content management system bans all cached content with a specific tag when that tag is modified[2][6].
4. Time-to-Live (TTL) Expiration
Description: Sets a time-to-live value for cached content. Once the TTL expires, the content is considered stale and must be refreshed.
Use Case: Ideal for content that changes periodically.
Example: A weather website sets a 1-hour TTL for its forecast data to ensure users receive up-to-date information[4][7].
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