SQLite + FTS5

A high-performance full-text search engine built directly into the SQLite database core.

FTS5 transforms SQLite into a sophisticated search engine by providing virtual tables for lightning-fast prefix searches and proximity queries. It leverages a highly optimized inverted index structure (similar to Lucene) to handle millions of rows with millisecond latency. Developers get advanced features like BM25 ranking, custom tokenizers, and the 'MATCH' operator without leaving the SQL interface. It is the gold standard for adding local search to mobile apps, desktop software, and edge computing environments where external dependencies like Elasticsearch are overkill.

https://www.sqlite.org/fts5.html