Ledger is a distributed storage system for Fuchsia.
Each application (or more precisely, each component) running on behalf of a particular user has a separate data store provided and managed by Ledger, and vended to a client application by Fuchsia framework through its component context.
The data store for the particular component/user combination is private - not accessible to other apps of the same user, and not accessible to other users of the same app.
Each data store is transparently synchronized across devices of its user through a cloud provider. Any data operations are made offline-first with no coordination with the cloud. If concurrent modifications result in a data conflict, the conflict is resolved using an app-configurable merge policy.
Each data store is organized into collections exposing a key-value store API called pages. Page API supports storing data of arbitrary size, atomic changes across multiple keys, snapshots and modification observers.
Documentation for using Ledger:
Documentation for integrating with Ledger in client apps:
Documentation for setting up a remote Cloud sync provider:
Documentation for developing Ledger: