Real-time web apps with mongodb and nodejs

We built a real-time app last year, basically a tool for authors to work on the same page where they could add/remove/edit elements (text, images, videos, etc.)

What we used were:

• Node.js, with Hapi.js framework (express based)
• Socket.io
• No MongoDB but the awesome RethinkDB instead, which is real-time by default and basically uses listeners to tell you whenever something has changed. (mongoDB sucks in our opinion, we used it in the past and it feels like "never again", but that's our opinion)
• React/Redux in order to update the DOM only for elements that have changed, Angular with its both-ways wouldn't have worked well in our opinion, since several users may modify the same page at the same time and therefore re-rendering all the elements would cause to lose the focus.

And honestly, it's pretty awesome how fast it is.

This is easy to solve without much of complication and saving documents to databases. You should only save document locations. Node has some very awesome features built for this kind of applications. I recommend you to look into these topics:

• EventEmitters

• Streams

Node filesystem has classes that you can use to build this for documents:

• fs.FSWatcher

• fs.ReadStream

• fs.WriteStream

You can use socket.io to hook up these events to your client application.

I would go with option 1 & 3 but with slight difference.1. The first option to tail mongoDB opLog is a good one but the overhead becomes very big on the DB where your app will be making millions of transactions. The meteorJS library is already doing this and you can explore them as they are mature and stable to use than writing our own services.

3. Option 3 to use socket.io. You can actually use socket.io for publishng changes as well as writing to database if you are using rethinkDB which supports native changefeeds. Native changefeeds meaning, everytime there is a write to the table/collection that you want to watch realtime, it gives a callback with the old and new data where you can use socket.io to publish to all clients.
4. Another way to do it which is a more robust solution is using rabbitMQ like how Paul had mentioned above.