/latest/ Link to Your Newest Post

// /latest/ opens your newest post; /latest/news/ opens the newest post in the News category.
$wpide_latest_path = 'latest';

add_action( 'template_redirect', function () use ( $wpide_latest_path ) {
    // Only when no real page uses the address.
    if ( ! is_404() ) {
        return;
    }

    $path = isset( $_SERVER['REQUEST_URI'] ) ? (string) wp_parse_url( wp_unslash( $_SERVER['REQUEST_URI'] ), PHP_URL_PATH ) : '';
    $base = untrailingslashit( (string) wp_parse_url( home_url( '/' . trim( $wpide_latest_path, '/' ) ), PHP_URL_PATH ) );

    if ( '' === $path || ( strtolower( untrailingslashit( $path ) ) !== strtolower( $base ) && 0 !== stripos( $path, $base . '/' ) ) ) {
        return;
    }

    $category = sanitize_title( trim( substr( $path, strlen( $base ) ), '/' ) );
    $cache    = get_transient( 'wpide_latest_posts' );
    $cache    = is_array( $cache ) ? $cache : array();
    $post_id  = isset( $cache[ $category ] ) ? (int) $cache[ $category ] : null;

    if ( null === $post_id ) {
        $args = array(
            'post_type'           => 'post',
            'posts_per_page'      => 1,
            'has_password'        => false,
            'ignore_sticky_posts' => true,
            'no_found_rows'       => true,
            'fields'              => 'ids',
        );

        if ( '' !== $category ) {
            $args['category_name'] = $category;
        }

        $ids     = get_posts( $args );
        $post_id = $ids ? (int) $ids[0] : 0;

        // Keep at most 50 category answers in the cache.
        $cache[ $category ] = $post_id;
        set_transient( 'wpide_latest_posts', array_slice( $cache, -50, null, true ), DAY_IN_SECONDS );
    }

    if ( ! $post_id ) {
        return;
    }

    nocache_headers();
    wp_safe_redirect( get_permalink( $post_id ), 302 );
    exit;
}, 1 );

// Forget the cached answers whenever a post is published, updated or removed.
add_action( 'transition_post_status', function ( $new_status, $old_status, $post ) {
    if ( 'post' === $post->post_type && ( 'publish' === $new_status || 'publish' === $old_status ) ) {
        delete_transient( 'wpide_latest_posts' );
    }
}, 10, 3 );