This app is written in Java from a Parallel Universe where annotations were never invented. You can check: there isn't a single annotation in this codebase!
It requires a JDK 11 to build and run.
It's a showcase for my talk, Java from a Parallel Universe. It's also a fully functioning Todo Backend (you can run the Todo Backend test suite!), using the Spark web framework, the Jdbi database framework, and no framework for dependency injection because you really really don't need one. It also uses Java 11 var declarations, Vavr and Polyglot for Maven because I think they're pretty nifty and because they make the code look a little different, as if, I dunno, as if it came from a Parallel Universe or something? Also, the application is fully modularized and has 100% test coverage because why not.
Note, however, that this is still a demo app that is not production-ready. Some corners have definitely been cut. For example, the InMemoryRepository is not thread-safe.