System Design Fundamentals
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Cache Invalidation

Cache Invalidation Strategies

While caching can significantly improve performance, we must ensure that the data in the cache is still correct—otherwise, we serve out-of-date (stale) information. This is where cache invalidation comes in.

  1. Ensure Data Freshness
    • When the underlying data changes—say a product’s price updates in your database—you must mark or remove the old (cached) data so users don’t see stale information. This process is called “cache invalidation.”

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M

mayank190804

· 2 years ago

Please help

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M

mbliss398

· 3 years ago

When data is written to the permanent datastore in the write-around scheme, is any stale data in the cache purged?

Ex:

  • Item A has price of $20, stored in cache and DB

  • Item A goes on sale, write-around strategy sets price to $10 in DB

  • Client requests item A's price immediately after DB update, do they read the $20 value from the cache or does this trigger a cache miss and get the $10 from the DB?

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Mat Wilk

Mat Wilk

· a year ago

Isn't it just writing to the perm storage strategies and not invalidation strategies, they don't necessarily invalidating the cache, it's super confusing and I think the naming in this post should be changed

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Vaishnavi Ainapure

Vaishnavi Ainapure

· 5 months ago

How does a request know that a given data is stale? Is there any flag marked against each object or entity to indicate it is stale?

Sourav Singh

Sourav Singh

· 2 years ago

Can you cite some example where Write Back or Write Cache caching mechanism are suitable to use?