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SELECT 
  b.row 
FROM 
  (
    SELECT 
      product_id, 
      @r := @r + 1 as row 
    FROM 
      (
        SELECT 
          products.product_id 
        FROM 
          cscart_products as products 
          LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
          AND descr1.lang_code = 'en' 
          LEFT JOIN cscart_product_prices as prices ON prices.product_id = products.product_id 
          AND prices.lower_limit = 1 
          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 shared_descr.product_id = products.product_id 
          AND shared_descr.company_id = 1 
          AND shared_descr.lang_code = 'en' 
          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 
          1 
          AND cscart_categories.category_id IN (450) 
          AND cscart_categories.company_id = 1 
          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 prices.usergroup_id IN (0, 0, 1) 
        GROUP BY 
          products.product_id 
        ORDER BY 
          descr1.product asc
      ) AS a
  ) AS b 
WHERE 
  b.product_id = 672

Query time 0.00112

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	<derived2>	ALL					15	Using where
2	DERIVED	<derived3>	ALL					15
3	DERIVED	cscart_categories	const	PRIMARY,c_status,p_category_id,idx_category_id	PRIMARY	3	const	1	Using temporary; Using filesort
3	DERIVED	products_categories	ref	PRIMARY,pt	PRIMARY	3	const	15	Using where; Using index
3	DERIVED	products	eq_ref	PRIMARY,status	PRIMARY	3	mahm3t_cs443.products_categories.product_id	1	Using where
3	DERIVED	cscart_aval_statuses	eq_ref	PRIMARY	PRIMARY	4	mahm3t_cs443.products.aval_status	1
3	DERIVED	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
3	DERIVED	prices	ref	usergroup,product_id,lower_limit,usergroup_id	usergroup	3	mahm3t_cs443.products_categories.product_id	1	Using where; Using index
3	DERIVED	descr1	eq_ref	PRIMARY,product_id	PRIMARY	9	mahm3t_cs443.products_categories.product_id,const	1	Using where

Result

row