Comment by mateiz

Yup, this is a great explanation. Cuckoo hashes actually do much better in terms of load if you use buckets with multiple items, as we did here. The classical one with one item per location can get "stuck" with unresolvable cycles between elements at 50% load, but when you have these buckets, there are many more ways to resolve collisions, which lets you greatly increase the load. 99% is extreme but definitely doable. Writing a fuller post on this is definitely a good idea -- we may do it in the future.