This skill should be used when the user designs a "search system", needs "full-text search", asks about an "inverted index", "Elasticsearch / OpenSearch", "relevance ranking" (TF-IDF/BM25), "search autocomplete / typeahead", an "indexing pipeline", or "faceted search". It gives the crawl/index/search architecture, index sharding and replication, ranking, and near-real-time indexing. Use it whenever users must query text by relevance rather than fetch rows by key, even if they don't say "search engine".
