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Late-Interaction Retrieval (ColBERT)

A bi-encoder crushes a document into one vector and loses which words carried the meaning. A cross-encoder keeps everything but cannot precompute, so it only reranks. Late interaction keeps one vector per token and compares them at query time, buying most of the accuracy of the second at roughly the scan cost of the first, and paying for it in storage.

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RELATED CONCEPTS

Reranking and Two-Stage Retrieval Hybrid Search (Lexical + Vector)Embeddings & Vector Representations Vector Databases Approximate Nearest Neighbor (ANN)

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