Separating data from code in Puppet modules is advisable as it improves reusability of code. The separation can be accomplished with Hiera by having separate levels based on facts, organizational units, locations, etc.

Hiera can also be used for storing private data that needs to be protected and must not be readable by outsiders. Typically the data, like all other code, is stored in a version control system that may be located outside the organisation. In such a case Hiera encryption is a must.