Duplicate Queries

Generally speaking, you could use the WP Transients API to save the query. 

// Get any existing copy of our transient data
if ( false === ( $special_query_results = get_transient( 'special_query_results' ) ) ) {
    // It wasn't there, so regenerate the data and save the transient
     $special_query_results = new WP_Query( 'cat=5&order=random&tag=tech&post_meta_key=thumbnail' );
     set_transient( 'special_query_results', $special_query_results, 12 * HOUR_IN_SECONDS );
}

// Use the data like you would have normally...

This article brings up a good point by arguing that it’s not a good idea to store a WP_Query() object as a transient, and instead suggests storing the post IDs returned from an expensive query in a transient, then using those IDs to create a new WP_Query. Granted, with this approach we’d be right back to having duplicate queries, but they would be lighter queries.

$cache_key = 'my-expensive-query';
if ( ! $ids = get_transient( $cache_key ) ) {
    $query = new WP_Query( array(
        'fields' => 'ids',
        // ...
    ) );

    $ids = $query->posts;
    set_transient( $cache_key, $ids, 24 * HOUR_IN_SECONDS );
}

$query = new WP_Query( array(
    'post__in' => $ids,
) );

// while ( $query->have_posts() ) ...

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