Scaling Hierarchical Navigable Small World (HNSW) Vector in Redis

if you have different vectors about the same use case split in different instances / keys, you can ask VSIM for the same query vector into all the instances, and add the WITHSCORES option (that returns the cosine distance) and merge the results client-side, and you have magically scaled your hundred of millions of vectors into multiple instances, splitting your dataset N times
— Read on simonwillison.net/2025/Nov/11/scaling-hnsws/