Extensibility as a key part of a modern PaaS
  Another key part of a modern PaaS is extensibility.
  Currently, 
63 %
  of the vendors are 
extensible.
  Originally developed by Heroku, 
buildpacks are a collection of
  scripts that define a generic API for detecting, compiling and releasing e.g. runtime languages or frameworks.
  Buildpacks enable the developers to add own packages of services or runtimes to their PaaS environment. Other vendors have either adopted Heroku’s buildpacks or
  defined their own extensibility mechanisms. This capability gives the developers greater freedom and possibilities to configure the system, blurring the differentiation to IaaS.