I will being streaming "Cache Invalidation Isn't Hard" at http://twitch.tv/handmade_hero shortly. The topic of this lecture will be that cache invalidation isn't hard, and will include discussions on cache invalidation and it's not-being-hard-ness.
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Replying to @cmuratori
I'm still in the middle of the stream but the answer seems to be: It's either trivial or impossible. If you cache the output of a "pure" function, cache invalidation is not a thing. If you cache the output of a changing function, just forget about it.
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Replying to @hasen_judy @cmuratori
I think the context in which "cache invalidation is hard" is something where the output can change but you can also know when it will change so you can invalidate the entry in the cache. But managing that is a bit intricate and if you get it wrong the whole system is broken.
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I cover that at the end. But I also point out that it is not really that hard of a problem compared to others, because by definition you already have your "test" - you can call the function and the approximation on billions of inputs and test that the results match.
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