It seems the whole index is kept in RAM. Thus the index size is limited by the amount of RAM available. This explains the impressive indexing and search performance (1M blog 500M data 28 seconds index finished, 1.65 ms search response time, 19K search QPS) The Persistent storage data is stored to the hard disk solely when the program closes. The data is then restored from the hard disk when the program restarts ( https://github.com/go-ego/riot/blob/master/docs/zh/persisten... ). This is a limited approach compared to Lucene/Solr/Elasticsearch LSM which handle high-volume inserts to its indexes with a log-structured merge-tree (LSM) and where the index size is only limited by the available hard disk space.