"Need" is always such a strong word, but Phoenix is particularly well-suited to real-time applications, and can scale pretty ridiculously off of them.

Not to mention, Elixir is a joy to code in, and a lot of us are still experimenting with it, trying to figure out where it's going. So projects like this are a good outlet.

Elixir compiles to bytecode for the Erlang VM/BEAM. Erlang + OTP = scalable/fault-tolerant distributed systems. Phoenix is closely coupled with OTP.

Not sure if Trello itself requires it or benefits from it, but any distributed system can benefit from this architecture.

I haven't hit their site yet, but I don't think they're saying you need Elixir to build this kind of project. I think it's more along the lines of needing Elixir to build a tutorial series for Elixir.

As for the benefits of using Elixir, I'm not qualified to answer that since I've only skimmed the surface of what Elixir is (but it looks intriguing!).

Trello has a certain real-time aspect to it that lends itself very well with Elixir channels. (At least I assume this tutorial is going to use that for the realtime bit). Rails is coming out with something as well, called ActionCable.

And finally Meteor has it with utmost simplicity as well. Just save to the database and Meteor updates the data to everyone, automatically.

This use of "need" makes me wonder what the earliest tech is that you could use to build a trello-ish. I'm thinking it's doable with C, CGI, and xmlhttprequest....

tongue in cheek, but check out Trello in 4096 bytes: http://danlec.com/blog/trello-in-4096-bytes

Or a more closer-to-the-metal solution like Node.js?

Joking aside, I wonder if it's possible to write a real-time webapp with C and CGI. Ok, 'possible' is a strong word; but I'd really like to hear from someone who'd given this a try.

Back in the mists of time, there was a thing called CGI-IRC written in perl that you deployed as an nph CGI script and would then do real time comms; I think (vague memory) the original authors an ircatwork.com using it and then eventually started mibbit.

I don't recall seeing one written in C, I think the last time I saw a CGI script written in C was a some years ago version of Nagios

Sure it would be. Wouldn't be terribly hard, either. Use normal CGI along with a library like libwebsockets.

Now, would I deploy it for production? Not likely.

There are a few web games & apps written in C that were posted to HN.

Why wouldn't it be?