A number of the built-in domain services uses this annotation, including Scratchpad and QueryResultsCache.

You may find that these services must be injected using the Provider idiom, not directly. For example:

@DomainService
public class SomeRepository {
   // ...
   @Inject Provider<QueryResultsCache> queryResultsCacheProvider;
}

If you forget to do this, then the framework will fail-fast with a suitable error message.