I have need to create an app that does three things-send bulk emails, bulk SMS and bulk voice calls. I am going to use Twilio for voice, one of the SMS providers and SMTP for emails. That data is delivered from an Asp.net web app.<p>I am wondering if I Node.js based service type app would be the best choice as I would like the service to be non-blocking and scalable.
I have to agree with the commenters. You should ultimately build on whatever you're comfortable with in order to get your product out the door. If you have to worry about optimization and scalability later, then you will have to cross that bridge when you get to it, but it is a good problem to have. Aside from that, I can say that Node.js is an ultra fast, low footprint platform. The amount of throughput that you can get out of node is pretty incredible.
You're probably worrying too much about scaling right now. Worry about supporting a few users with a minimum set of features first. Then go get those users. Then scale.<p>That said, node.js is awesome, and good for what you are looking for at least because it is very simple to set up and I hear it's quite scalable as well.
The hard part of scaling initially isn't the technology, it's getting the users at all. Build it on whatever you know today, and then if you're very lucky whatever choice you make will become a problem later.