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Muvera: Making multi-vector retrieval as fast as single-vector search

Muvera: Making multi-vector retrieval as fast as single-vector search

2 comments

·June 26, 2025
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trengrj

We added Muvera to Weaviate recently https://weaviate.io/blog/muvera and also have a nice podcast on it https://www.youtube.com/watch?v=nSW5g1H4zoU.

When looking at multi-vector / ColBERT style approaches, the embedding per token approach can massively increase costs. You might go from a single 768 dimension vector to 128 x 130 = 16,640 dimensions. Even with better results from a multi-vector model this can make it unfeasible for many use-cases.

Muvera, converts the multiple vectors into a single fixed dimension (usually net smaller) vector that can be used by any ANN index. As you now have a single vector you can use all your existing ANN algorithms and stack other quantization techniques for memory savings. In my opinion it is a much better approach than PLAID because it doesn't require specific index structures or clustering assumptions and can achieve lower latency.

dinobones

So this is basically an “embedding of embeddings”, an approximation of multiple embeddings compressed into one, to reduce dimensionality/increase performance.

All this tells me is that: the “multiple embeddings” are probably mostly overlapping and the marginal value of each additional one is probably low, if you can represent them with a single embedding.

I don’t otherwise see how you can keep comparable performance without breaking information theory.