Fanout vs Radar: What are the differences?

Developers describe Fanout as "Realtime APIs made simple". Fanout makes it easy to build realtime APIs and apps. The product is a cross between a reverse proxy and a message broker. Receivers subscribe to channels, and published data is delivered in realtime. On the other hand, Radar is detailed as "High level API and backend for writing web apps that use push messaging". Radar is built on top of engine.io, the next-generation backend for socket.io. It uses Redis for backend storage, though the assumption is that this is only for storing currently active data.

Fanout and Radar belong to "Realtime Backend / API" category of the tech stack.

Some of the features offered by Fanout are:

• Reverse proxy -- integrate realtime with any level of your technology stack, not just your front end.
• Interoperable -- Add realtime to any API, no matter your backend or database, without changing any of your existing API contracts.
• Open -- cloud or self hosted, it’s up to you. We don’t believe in vendor lock-in.

On the other hand, Radar provides the following key features:

• More than just pub/sub: a resource-based API for presence, messaging and push notifications via a Javascript client library
• Written in Javascript/Node.js, and uses engine.io (the new, low-level complement to socket.io)
• Backend to multiple front-facing servers

Radar is an open source tool with 209 GitHub stars and 35 GitHub forks. Here's a link to Radar's open source repository on GitHub.