The use of the PostgreSQL engine is optional. However, if the engine is deficient or not installed, some functionalities will be inaccessible or will no longer be provided
Personal categories: If you use your own categories, the PostgreSQL engine can store a large amount of data, i.e. millions of websites ordered by theme.
Statistics: Access statistics (HTTP or DNS) use the SQL engine.
Fingerprinting Web Access: Web access control through fingerprinting stores fingerprints and rules inside the PostgreSQL engine.