There are also approaches do doing the filtering while traversing a vector index (not just pre/post) e.g. this paper by microsoft explains an approach https://dl.acm.org/doi/10.1145/3543507.3583552 which pgvectorscale implements here: https://github.com/timescale/pgvectorscale?tab=readme-ov-fil...

In theory these can be more efficient than plain pre/post filtering.