- There are many scenarios in which a single buildpack is not sufficient when building an application. This includes cases when you need to: Run a buildpack for each language your app uses For example, run a JavaScript buildpack for assets and a Ruby buildpack for your application Run a daemon process such as pgbouncer with your application. Pull in system dependencies with apt. You can check the following for more information: https://devcenter heroku com/articles/using-multiple-buildpacks-for-an-app