You don\'t need to worry to much about your query as there is not much you can do about it. You can unfortunately not just only query categies, post titles and images natively using WP_Query. Post categories needs to be called separately inside the loop, just like featured images.

If you dig deeper into core, you will see that all postdata and post terms are cached, so when you think you are making extra db calls, you are not. The cache is first checked for the requires data, if it is, the data is retrieved from the cache, otherwise the db is queried and the data is cached for later queries.

You can add \'no_found_rows\' => true, to your arguments if you are not going to paginate your query. This makes the query faster as it ignores pagination. Alternatively, you can use get_posts which has this already build in

Also, you can make use of transients to store the result from a query and only flush the transient when a new post is added in a particular category or custom field