RAG & Agents
Reciprocal Rank Fusion (RRF)
Fusing ranked lists by summing 1/(k + rank) across systems, with k typically 60.
Why interviewers ask about it
Rank-based, so it needs no score normalisation - robust when BM25 scores are unbounded and cosine is in [−1, 1]. The safer default over weighted score fusion.
Related terms
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