GraphQL + SpringBoot + DataLoaders: what is the right pattern?

Question

I have GraphQL + SpringBoot + MongoDB application, with graphql.java.kickstart.springboot ,and I'm having performance issues. The walking skeleton of this application was done the last year and I received it as it is. I'd like to add DataLoaders / BatchDataLoaders (better) to improve the performance and to avoid to query the DB overtime for similar requests. Looking at DataLoaders examples I see quite different implementations from the one I have. I have a QueryResolver class that calls the Service which calls the Repository. The result is exposed from here, not handled by some Resolvers.

@Component
@Slf4j
@AllArgsConstructor
@NoArgsConstructor
public class Query implements GraphQLQueryResolver {
    @Autowired
    ProjectService projectService;

    public Iterable<ProjectDao> listProjects(String name, Sort orderByInput) {
        return projectService.getProjects(name, orderByInput);
    }
}

Now I don't understand if this is a wrong approach in order to add the DataLoaders. Here I found a question with a similar implementation, but then he seems to have changed looking at this answer. Changing the whole code would be time-consuming and I really hope I'm just missing something. Do you have any tips or docs to suggest? Thank you so much in advance!