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Hi, is tinder not storing the disliked (left swiped) information ? Otherwise, how will tinder know to not show the profile again to the user ?

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They do put the disliked profiles in S3 storage for extra data analysis. It's possible they store it in a cache or a data structure to prevent showing the same profile twice.

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Won't that require too much storage ? Storing all the pairs of likes and dislikes ? That is order of O(n^2). That's too much memory required ? How is tinder solving for that ?

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I'd assume they store the 'profile ID' in a hash data structure on the cache server.

Or it could also be a probabilistic data structure like bloom filter.

Yet I don't think the space complexity is O(n^2), probably each person dislikes a limited number of people compared to the total users of Tinder.

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stop asking awkward questions, the author of the article has no idea how it actually works

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