Solr is used as a full-text search database, often supplementing an SQL database in a typical Brightspot application. Containing the same data that is stored in the SQL database, Solr provides the superior text matching capabilities and compound-predicate query performance. However, SQL databases provide faster primary key lookups than Solr, and support atomic updates that were unavailable in Solr until the 4.0 version.
As a best practice, it is recommended that you use an SQL database and a Solr database concurrently via AggregateDatabase. For more information, see Database configuration.