Of course, you can't share multiple apps behind one domain, so if the one dyno isn't keeping you you'll need to scale up and pay for it.
OTOH, if you don't need to worry about any extra latency (maybe?) you could probably get away with a rails+node app like https://github.com/maccman/holla running free by having one app just run the web interface, and point the backend at another app running node.
As soon as you go outside of one tech stack it's cheaper to just get a small VPS to start with, but heroku definitely has its perks.
Of course, you can't share multiple apps behind one domain, so if the one dyno isn't keeping you you'll need to scale up and pay for it.
OTOH, if you don't need to worry about any extra latency (maybe?) you could probably get away with a rails+node app like https://github.com/maccman/holla running free by having one app just run the web interface, and point the backend at another app running node.
As soon as you go outside of one tech stack it's cheaper to just get a small VPS to start with, but heroku definitely has its perks.