Acquired by Apple in 2015, the FoundationDB database architecture has officially gone open source, the company announced today. It’s the latest move by Apple to open more of its non-secret software initiatives to public contributions, following earlier moves with its Swift programming language, cryptographic libraries, and benchmarking tools.

While FoundationDB is far from Apple’s best-known product, it’s the database underlying iCloud, Apple’s massive cloud-based server system for holding and synchronizing hundreds of millions of user accounts — plus trillions of pieces of data. Apple describes FoundationDB as a scalable “distributed datastore, designed from the ground up to be deployed on clusters of commodity hardware,” focusing on data consistency.

Why is Apple open-sourcing it? “We believe FoundationDB can become the foundation of the next generation of distributed databases,” the company said, explaining that the system consists of a simple core plus multiple layers specific to types of data and separate access patterns. “By open sourcing the FoundationDB core, we expect the quantity and variety of layers to develop rapidly,” creating an “ecosystem of layers” and an open community. After the announcement, an active discussion between the company’s founders and the community popped up today on Hacker News.

Apple is offering the source for FoundationDB at github.com/apple/foundationdb, with macOS, Windows, and Linux binary installers at www.foundationdb.org/download/. A Getting Started guide is also available on GitHub.