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Dev MaxxingAdvancedDistributed Systems90 sec
Cache invalidation
Cache invalidation is removing or updating cached data once it's known to be outdated, so future requests don't keep receiving stale results.
Prerequisite: Cache
What matters
Deciding exactly when to invalidate a cache is a genuinely hard problem, since invalidating too rarely serves stale data and invalidating too often loses most of the cache's benefit.
Example
Updating a product's price in the database might trigger invalidating that product's cached page, so the next request rebuilds it with the new price.
Common misconception
Cache invalidation is not a solved, purely mechanical step; deciding what to invalidate and when is widely regarded as one of the trickier problems in software design.
Recall question
Why is deciding exactly when to invalidate a cache considered a genuinely hard problem?
Keywords and related concepts
cache invalidationstale dataconsistencycache