Hybrid Retrieval Math

Why it matters

Hybrid is modern RAG standard. Understanding shapes design.

The architecture

Retrieve dense + sparse in parallel.

RRF or weighted fusion.

Deduplicate + rerank.

How it works end to end

RRF: sum 1 / (60 + rank_i).

Weighted: alpha * dense + (1-alpha) * sparse.

Combine with rerank.