realm by MongoDB

Realm’s mobile database is an open-source, developer-friendly alternative to CoreData and SQLite. Start in minutes, port your app in hours, and save yourself weeks of work. Realm’s object-oriented data model is simple to learn, doesn’t need an ORM, and lets you write less code. Realm’s local database persists data on-disk, so apps work as well offline as they do online. Realm is fully-featured, lightweight, and efficiently uses memory, disk space, and battery life. Realm was built for mobile developers, with simplicity in mind. The idiomatic, object-oriented data model can save you thousands of lines of code. Realm’s live objects mean data updated anywhere is automatically updated everywhere. If you need to freeze elements of your data for Reactive frameworks, you can do that, too.