If you are just using heroku to run a process it is pretty easy to rebuild on AWS. Here is one fairly solid guide: http://blog.clearbit.com/ec2-heroku/

Depending on what language you are using google's app engine could be a quick replacement.

http://rogerstringer.com/2015/05/13/make-your-own-heroku/

https://github.com/buttfoundry-community/bosh-buttfoundry/bl...

Another HN thread: https://news.ycombinator.com/item?id=4183634

I'm not a big fan of docker for a few irrelevant reasons but using it w/ heroku makes it very easy to migrate to other container hosts.

edit: the founder of Flynn replied to parent as well, that is also a great alternative that I forgot to include.