Comment by dimatura

I remember similar observations for an earlier use case in computer vision, loop closure and place recognition for visual SLAM algorithms. In this case the goal was to find a needle (or needles) in a big haystack of visual descriptors (in some sense, proto-embeddings for small image patches or in some cases, whole images). Several approaches used hierarchical data structures for the NN search such as k-mean trees. But linear search - especially with binary descriptors, also became popular as a fast and simple alternative.