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An offline-first database
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DeltaDB DeltaDB Build Status Coverage Status Dependency Status

DeltaDB is an offline-first database designed to talk directly to clients and works great offline and online.

** Update: Suspending Development of DeltaDB **

I have decided to suspend development of DeltaDB for the following reasons:

  • Recent enhancements to both PouchDB and CouchDB have made PouchDB initial replication much faster
  • After more analysis of the last-write-wins resolution policy, I am left feeling that the last-write-wins resolution policy is mostly good for real-time systems that are always online. In DeltaDB, this last-write-wins policy results in a Reasonable Ordering. Moreover, the last-write-wins policy is nice when starting a new project as it is automatic, but other conflict resolution policies that force the user to manually resolve the conflict, like CouchDB’s revision protocol, have become more of the standard in the offline-first world.
  • Building a DB that scales and is distributed over many nodes, takes a lot of work. I considered some of the necessary details when initially designing DeltaDB, but have only scratched the surface of what needs to be done. There are other DBs, like CouchDB 2.0, that have nearly solved these problems and CouchDB has been in development since 2005.

Live Demos

  • todomvc-angular - a todo app. For fun, open it in 2 different browser windows and watch the todos change in the 2nd window when you change the todos in the 1st window.

  • hello - a simple hello world example with code

Getting Started With DeltaDB

Check out the Getting Started With DeltaDB tutorial

Main Principles

  • Written in JavaScript
  • Framework agnostic
  • Works the same whether the client is offline or online
  • NoSQL database that works in your browser and automatically syncs with the database cluster
  • Stores all data as a series of deltas, which allows for smooth collaborative experiences even in frequently offline scenarios.
  • Uses a simple last-write-wins conflict resolution policy and is eventually consistent
  • Uses a homegrown ORM to speak to underlying SQL databases. (Support for underlying NoSQL databases will be added)
  • Is fast. Clients push their deltas on to the server's queue. The server processes the queue separately and partitions the data so that clients can retrieve all recent changes very quickly.
  • Implements a granular authentication system that protects databases, collections, docs and attributes
  • Is incredibly scalable. Deltas can be segmented by UUID and the cost to add new nodes has a negligible impact on the cluster as handshaking between servers can be done as frequently as desired.
  • Highly available. Clients can switch to talk to any node, even if that node hasn't received the latest deltas from another node.
  • Fault tolerant by using the concept of a quorum of servers for recording changes
  • Data is auto-restored when a client modifies data that was previously deleted
  • Uses timestamps to update records so that transactions and their overhead can be avoided
  • Thread-safe so that adding more cores will speed up DB reads and writes


Because it doesn't exist and true support for offline environments needs to be engineered from the ground up

  • PouchDB relies on CouchDB and CouchDB is slow to replicate when there are many revisions and it is not optimized for offline setups like db-per-user
  • Firebase doesn't work offline and is not open source
  • Meteor doesn't work offline
  • See Inspiration for more info









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