Retrieval
Hybrid search
Combining semantic and keyword search, because each finds things the other misses.
Semantic search finds meaning; keyword search finds exact strings. A customer asking about "the thing that keeps jamming" needs the first. A customer quoting invoice INV-88231 needs the second.
Hybrid search runs both and merges the results, typically with a technique called Reciprocal Rank Fusion that blends the two rankings without needing the scores to be comparable.
This is one of the highest-value, least glamorous improvements available to a RAG system. Teams that skip it usually discover the gap the first time someone searches for a serial number.