A hybrid retrieval system has been developed to efficiently serve over 127,000 queries on a single AWS Lightsail instance, combining the precision of BM25 with the semantic understanding of FAISS. This system operates without a GPU for embeddings, though a GPU can be used optionally for reranking to achieve a 3x speedup. The infrastructure is cost-effective, running on a t3.medium instance for approximately $50 per month, and achieves 91% accuracy, significantly outperforming dense-only methods. The hybrid approach effectively handles complex queries by using a four-stage cascade that combines keyword precision with semantic understanding, optimizing latency and accuracy through asynchronous parallel retrieval and batch reranking. This matters because it demonstrates a cost-effective, high-performance solution for query retrieval that balances precision and semantic understanding, crucial for applications requiring accurate and efficient information retrieval.
