Sandbox

SELECT 
  cscart_product_filters.filter_id, 
  cscart_product_features_values.variant_id 
FROM 
  cscart_product_features_values 
  LEFT JOIN cscart_products as products ON products.product_id = cscart_product_features_values.product_id 
  LEFT JOIN cscart_product_filters ON cscart_product_filters.feature_id = cscart_product_features_values.feature_id 
  LEFT JOIN cscart_product_features ON cscart_product_features.feature_id = cscart_product_features_values.feature_id 
  INNER JOIN cscart_products_categories as products_categories ON products_categories.product_id = products.product_id 
  INNER JOIN cscart_categories ON cscart_categories.category_id = products_categories.category_id 
  AND (
    cscart_categories.usergroup_ids = '' 
    OR FIND_IN_SET(
      0, cscart_categories.usergroup_ids
    ) 
    OR FIND_IN_SET(
      1, cscart_categories.usergroup_ids
    )
  ) 
  AND cscart_categories.status IN ('A', 'H') 
  LEFT JOIN cscart_ult_product_descriptions shared_descr ON products.product_id = shared_descr.product_id 
  LEFT JOIN cscart_aval_statuses ON cscart_aval_statuses.aval_status_id = products.aval_status 
  LEFT JOIN cscart_aval_statuses_descr ON cscart_aval_statuses.aval_status_id = cscart_aval_statuses_descr.aval_status_id 
  AND cscart_aval_statuses.status = 'A' 
  AND cscart_aval_statuses_descr.lang_code = 'en' 
  LEFT JOIN cscart_product_popularity as popularity ON popularity.product_id = products.product_id 
WHERE 
  cscart_product_filters.filter_id IN (13) 
  AND cscart_product_features_values.feature_id IN (30) 
  AND cscart_product_features_values.lang_code = 'en' 
  AND cscart_categories.category_id IN (838) 
  AND cscart_categories.company_id = 2 
  AND (
    products.usergroup_ids = '' 
    OR FIND_IN_SET(0, products.usergroup_ids) 
    OR FIND_IN_SET(1, products.usergroup_ids)
  ) 
  AND products.status IN ('A') 
  AND cscart_product_features.feature_type IN ('S', 'M', 'E') 
GROUP BY 
  cscart_product_features_values.variant_id

Query time 1.50638

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	cscart_product_filters	const	PRIMARY,feature_id,feature_id_status_idx,filter_id_idx,feature_filter_idx	PRIMARY	3	const	1	Using temporary; Using filesort
1	SIMPLE	cscart_product_features	const	PRIMARY	PRIMARY	3	const	1
1	SIMPLE	cscart_categories	const	PRIMARY,c_status,p_category_id,idx_category_id	PRIMARY	3	const	1
1	SIMPLE	products_categories	ref	PRIMARY,pt,product_id_idx,category_id_idx,product_category_idx,category_product_idx	PRIMARY	3	const	8	Using index
1	SIMPLE	products	eq_ref	PRIMARY,status,product_id_idx,status_idx	PRIMARY	3	mahm3t_cs443.products_categories.product_id	1	Using where
1	SIMPLE	cscart_product_features_values	ref	PRIMARY,fl,lang_code,product_id,fpl,product_id_idx,feature_id_idx,feature_value_product_idx,product_feature_idx	PRIMARY	6	const,mahm3t_cs443.products_categories.product_id	5	Using where; Using index
1	SIMPLE	shared_descr	ref	PRIMARY,product_id	product_id	3	mahm3t_cs443.products_categories.product_id	11	Using index
1	SIMPLE	cscart_aval_statuses	eq_ref	PRIMARY	PRIMARY	4	mahm3t_cs443.products.aval_status	1
1	SIMPLE	cscart_aval_statuses_descr	ref	aval_status_id	aval_status_id	10	mahm3t_cs443.cscart_aval_statuses.aval_status_id,const	1	Using where; Using index

Result

filter_id	variant_id
13	5935