Bloom filters are [one of?] the most used 'negative cache' structures. Consulting a bloom filter can give a decisive answer that a key is not in a collection (i

Bloom filters are [one of?] the most used 'negative cache' structures. Consulting a bloom filter can give a decisive answer that a key is not in a collection (ie. a key was never hashed). You can then avoid a (supposedly more expensive) lookup. I used bloom filters often in my database work. I was not familiar with cockoo filters (I am familiar with cockoo hash though), using them as a 'better bloom' seems to be a relatively new development. A quick googling found 'Cuckoo Filter: Practically Better Than Bloom' [https://www.cs.cmu.edu/~dga/papers/cuckoo-conext2014.pdf https://www.cs.cmu.edu/~dga/papers/cuckoo-conext2014.pdf].