The Docker API version continues to be independent of the
Docker platform version and the API version does not
change from Docker 1.13.1 to Docker 17.03. Even with the
faster release pace, Docker will continue to maintain
careful API backwards compatibility and deprecate APIs and
features only slowly and conservatively. And in Docker
1.13 introduced improved interoperability between clients
and servers using different API versions, including
dynamic feature negotiation.
- https://blog.docker.com/2017/03/docker-enterprise-edition/
What are you looking for here? Larger build dynos? Heroku provides the build service for free so we use perf-m dynos to get fast builds with reasonable cost (for us).