The question may sound funny but I think this should be possible.
What I want is to use a repository that is purely custom but is exposed just like a Repository. Thi
I've ended up writing spring-data-custom to create fully customized spring-data repositories, allowing custom code to be used with spring-data-rest etc.
@EnableCustomRepositories)@Custom)CustomRepository)Custom suffixImpl prefixfindOne, save, findAll, delete (see DefaultCrudMethods)@Queryspring-data-rest(copied from README)
As @wwadge correctly mentioned, spring-data-keyvalue is an alternative. Repositories have to implement KeyValueAdapter, e.g. MapKeyValueAdapter.