Here's an interesting approach to work with env variables proposed by Marijn Huizendveld
Frameworks offer tools to parameterize environments in a variety of ways. But because of this configuration files of projects tend to get messy once projects are taken into production. Specifying purpose of the parameter within the name can help identify unneeded configurations. Making configuration explicit within the application layer can be even more helpful. Doing so eases refactoring and provides potential to improve the overall developer experience.