Solr is the popular, blazing fast, open source NoSQL search platform from the Apache Lucene project. Its major features include powerful full-text search, hit highlighting, faceted search and analytics, rich document parsing, geospatial search, extensive REST APIs as well as parallel SQL. Solr is enterprise grade, secure and highly scalable, providing fault tolerant distributed search and indexing, and powers the search and navigation features of many of the world's largest internet sites.
Solr is written in Java and runs as a standalone full-text search server. Solr uses the Lucene Java search library at its core for full-text indexing and search, and has REST-like JSON APIs that make it easy to use from virtually any programming language. Solr's powerful configuration APIs and files allows it to be tailored to almost any type of application without Java coding, and it has an extensive plugin architecture when more advanced customization is required.
This is the official documentation for Apache Solr 9.0.0.