suppose there are four classes
class Product {

private Long productId;

}

class ProductImage {

private Long productId;

private Long productImageId;

}

class ProductAttachment {

private Long productId;

private Long productAttachmentId;

}

class ProductDto extends Product {

private List<ProductImage> images;

private List<ProductAttachment> productAttachments;

}

in the micro-service architecture, the service interface is designed as follows:
1 Fine granularity: provide three separate interfaces, which are called by other services to obtain data, and return directly to the front end
interface ProductService {

after the Api gateway aggregates and synthesizes the ProductDto.

Product getProduct(Long productId);

List<ProductImage> listProductImage(Long productId);

List<ProductAttachment> listProductAttachment(Long productId);

}
2 coarse granularity: provides an aggregation interface, which is called by other services, and the Api gateway only forwards and returns to the front end
interface ProductService {

ProductDto getProduct(Long productId);

}

which way do you prefer, and how to grasp the interface granularity of the service layer?