@Repository
public interface GooglePlayGamesRepository extends MongoRepository <GooglePlayGame, String> {

    GooglePlayGame findByTitleIgnoreCase(String gameTitle);

    @Aggregation("{$sample: {size: ?0} }")
    List<GooglePlayGame> findRandomGames(Long amount);

    List<GooglePlayGame> findByTitleContainsIgnoreCase(String gameTitle);

}

import org.springframework.data.annotation.Id;

@Document(collection = "googleplaygames")
@Getter
@Component
public final class GooglePlayGame implements Serializable {

    @Id
    String title; //это уникальный ключ!
    String genre;
    String price;
...
}

org.springframework.dao.DuplicateKeyException: E11000 duplicate key error collection: 5ef31a21233f9c398f473c6e_botapi.googleplaygames index: title dup key: { title: null };

import org.bson.types.ObjectId;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.index.Indexed;

...

@Id
ObjectId id;
@Indexed(unique = true)
String title;