Since sbt instances are separated in their own docker containers, they don't share an artifact cache. Also, when we deploy a new container, all the artifact cache is thrown away.
Sbt Docs:
http://www.scala-sbt.org/0.13/docs/Proxy-Repositories.html
Manual Steps
1. Install artifactory
2. Add remote repository [2]
(ivy) typesafe-ivy-releases: http://repo.typesafe.com/typesafe/ivy-releases/
(ivy) sbt-plugin-releases: https://dl.bintray.com/sbt/sbt-plugin-releases/
3. Create two virtual repositories [3]
scastie-ivy (with typesafe-ivy-releases and sbt-plugin-releases)
scastie-maven (with maven-central)
4. suppress POM consistency checks for maven-central [4] [4a]
[2]: http://scala-webapps.epfl.ch:8081/artifactory/webapp/#/admin/repositories/remote
[3]: http://scala-webapps.epfl.ch:8081/artifactory/webapp/#/admin/repository/virtual/new
[4]: http://scala-webapps.epfl.ch:8081/artifactory/webapp/#/admin/repository/remote/central/edit
[4a]: found in https://github.com/coursier/coursier/issues/286