SEO Sitemaps Slow MySQL queries

Yoast v7.5.1
WP v4.9.5

we are seeing poor performance in WP Admin related to slow MySQL queries generated by WPSEO_Sitemaps — here is an example with stack trace. What can be done to improve the performance of these queries?

SELECT l.ID, post_title, post_content, post_name, post_parent, post_author, post_modified_gmt, post_date, post_date_gmt
			FROM (
				SELECT wp_posts.ID
				FROM wp_posts
                        WHERE wp_posts.post_status = ?
			AND wp_posts.post_type = ?
			AND wp_posts.post_password = ?
			AND wp_posts.post_date != ?
		
					
				ORDER BY wp_posts.post_modified ASC LIMIT ? OFFSET ?
			)
			o JOIN wp_posts l ON l.ID = o.ID 

…d at /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
wp-db.php (1924)
…d at /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
wp-db.php (1813)
…d at /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
wp-db.php (2488)
…ent/mu-plugins/wordpress-seo/inc/sitemaps/
class-post-type-sitemap-provider.php (538)
…ent/mu-plugins/wordpress-seo/inc/sitemaps/
class-post-type-sitemap-provider.php (237)
…c57eb/code/wp-content/mu-plugins/wordpress-seo/inc/sitemaps/
class-sitemaps.php (326)
…c57eb/code/wp-content/mu-plugins/wordpress-seo/inc/sitemaps/
class-sitemaps.php (292)
…c57eb/code/wp-content/mu-plugins/wordpress-seo/inc/sitemaps/
class-sitemaps.php (270)
…c57eb/code/wp-content/mu-plugins/wordpress-seo/inc/sitemaps/
class-sitemaps.php (228)
in WPSEO_Sitemaps::redirect called at ? (?)
…v/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
class-wp-hook.php (286)
…v/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
class-wp-hook.php (310)
… at /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
plugin.php (515)
…/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
class-wp-query.php (1634)
…/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
class-wp-query.php (3230)
…t /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
class-wp.php (599)
…t /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
class-wp.php (715)
… /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/wp-includes/
functions.php (960)
…lled at /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/
wp-blog-header.php (16)
…equire called at /srv/bindings/8835655bbfb54ad2b687bd1c6eec57eb/code/
index.php (17)