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+
+# Search API
+
+The Elasticsearch indices used to power metadata search, statistics, and graphs
+on the fatcat web interface are exposed publicly at
+`https://search.fatcat.wiki`. Third parties can make queries using the
+Elasticsearch API, which is well documented online and has client libraries in
+many programming languages.
+
+A thin proxy (`es-public-proxy`) filters requests to avoid expensive queries
+which could cause problems for search queries on the web interface, but most of
+the Elasticsearch API is supported, including powerful aggregation queries.
+
+There is a short delay between updates to the fatcat catalog (via the main API)
+and updates to the search index.
+
+Notable indices include:
+
+- `fatcat_release`: release entity metadata
+- `fatcat_container`: container entity metadata
+- `fatcat_ref`: reference graph
+
+Schemas for these indices can be fetched directly from the index (eg,
+`https://search.fatcat.wiki/fatcat_release/_mapping`), and are versioned in the
+fatcat git repository under `fatcat:extra/eleasticsearch/`. They are a
+simplification and transform of the regular entity schemas, and include some
+synthesized fields (such as "preservation status" for releases). Note that the
+search schemas are likely to change over time with less notice and stability
+guarantees than the primary catalog API schema.