SleekDB - A Pure PHP NoSQL Document Database SleekDB is a simple document based NoSQL database that store data in plain JSON files. It is not designed for heavy-load IO operations, it is designed to have a simple solution for managing few gigabytes of data. SleekDB works great as the database engine for most low to medium traffic websites. Any site that gets fewer than 50k to 100K hits/day should work fine with SleekDB.