[bdupras]

Yes, cuckoo filters and counting bloom filters can start rejecting insertions before the filter is loaded - cuckoos because of the inability to find an open slot, and counting blooms because of saturation of a counter. Note that this is only the case if deletion or counting support are required.

In some cases, like the when there's a high likelihood of duplicate entries, this can represent a catastrophic failure mode. This is a good point, and when I get around to updating the tutorial, I'll make note of this.

Regarding the failure mode, an insertion can be knowingly rejected without mutating the filter, so the filter remains useful for subsequent insertions and all reads, retaining all its guarantees. The only loss is the rejection of the item - in our case we used this as signal to rebuild the filter at a larger size.