Rename Configuration methods returning Optional to use the pattern findXXX().
The Configuration interface has two methods to return each value type: a getXXX() method that will throw an exception if the key is not found; and a getOptionalXXX() method that returns an Optional<>. It will be a better convention to use findXXX() for the methods that return Optional<>. See e.g. Naming Optional query methods in Stephen Colebourne's blog.