I keep looking for a reason to write software using a proper DI container framework. In talking to Java devs most of them just mention injecting mocks for your database. You don't really need a full DI container for that you could use a service locator instead or some even lighter DI pattern. If you have that particular hammer though and know how to use it, then it becomes easy to achieve and use config to inject your backend.

But that's a long way from glorious full DI containers where you never call 'new' in your code anywhere and all object creation can be dictated by config. I suspect that must be only the kind of thing that people who maintain 1,000,000 line codebases that are at the center of massive bureaucracies.