SELECT 
  SQL_CALC_FOUND_ROWS (
    CASE WHEN products.parent_product_id <> 0 THEN products.parent_product_id ELSE products.product_id END
  ) AS product_id, 
  descr1.product as product, 
  companies.company as company_name, 
  GROUP_CONCAT(
    products.product_id 
    ORDER BY 
      products.parent_product_id ASC, 
      products.product_id ASC
  ) AS product_ids, 
  GROUP_CONCAT(
    products.product_type 
    ORDER BY 
      products.parent_product_id ASC, 
      products.product_id ASC
  ) AS product_types, 
  GROUP_CONCAT(
    products.parent_product_id 
    ORDER BY 
      products.parent_product_id ASC, 
      products.product_id ASC
  ) AS parent_product_ids, 
  products.product_type, 
  products.parent_product_id, 
  products.master_product_offers_count, 
  products.master_product_id, 
  products.company_id, 
  products.original_vendor_id, 
  IF(
    products.age_verification = 'Y', 
    'Y', 
    IF(
      cscart_categories.age_verification = 'Y', 
      'Y', cscart_categories.parent_age_verification
    )
  ) as need_age_verification, 
  IF(
    products.age_limit > cscart_categories.age_limit, 
    IF(
      products.age_limit > cscart_categories.parent_age_limit, 
      products.age_limit, cscart_categories.parent_age_limit
    ), 
    IF(
      cscart_categories.age_limit > cscart_categories.parent_age_limit, 
      cscart_categories.age_limit, cscart_categories.parent_age_limit
    )
  ) as age_limit, 
  descr1.full_description as full_description, 
  descr1.short_description as short_description 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'de' 
  LEFT JOIN cscart_product_prices as prices ON prices.product_id = products.product_id 
  AND prices.lower_limit = 1 
  LEFT JOIN cscart_companies AS companies ON companies.company_id = products.company_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') 
  AND cscart_categories.storefront_id IN (0, 1) 
  LEFT JOIN cscart_warehouses_sum_products_amount as war_sum_amount ON war_sum_amount.product_id = products.product_id 
  LEFT JOIN cscart_warehouses_destination_products_amount AS warehouses_destination_products_amount ON warehouses_destination_products_amount.product_id = products.product_id 
  AND warehouses_destination_products_amount.destination_id = 11 
  AND warehouses_destination_products_amount.storefront_id = 0 
  LEFT JOIN cscart_master_products_storefront_offers_count AS master_products_storefront_offers_count ON master_products_storefront_offers_count.product_id = products.product_id 
  AND master_products_storefront_offers_count.storefront_id = 1 
WHERE 
  1 
  AND cscart_categories.category_id IN (18) 
  AND (
    companies.status IN ('A') 
    OR products.company_id = 0
  ) 
  AND products.company_id IN (
    2, 3, 4, 7, 14, 15, 21, 23, 25, 26, 27, 28, 
    30, 33, 34, 36, 37, 38, 72, 73, 74, 78, 
    0
  ) 
  AND (
    (
      CASE products.is_stock_split_by_warehouses WHEN 'Y' THEN warehouses_destination_products_amount.amount ELSE products.amount END
    ) > 0 
    OR products.tracking = 'D'
  ) 
  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) 
  AND products.master_product_status IN ('A') 
  AND products.master_product_id = 0 
  AND (
    products.company_id > 0 
    OR (
      master_products_storefront_offers_count.count > 0
    )
  ) 
  AND products.product_type != 'D' 
GROUP BY 
  product_id 
ORDER BY 
  product asc, 
  products.product_id ASC 
LIMIT 
  24, 12

Query time 0.00349

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.421037539,
    "filesort": {
      "sort_key": "descr1.product, products.product_id",
      "temporary_table": {
        "filesort": {
          "sort_key": "case when products.parent_product_id <> 0 then products.parent_product_id else products.product_id end",
          "temporary_table": {
            "nested_loop": [
              {
                "table": {
                  "table_name": "cscart_categories",
                  "access_type": "const",
                  "possible_keys": ["PRIMARY", "c_status", "p_category_id"],
                  "key": "PRIMARY",
                  "key_length": "3",
                  "used_key_parts": ["category_id"],
                  "ref": ["const"],
                  "rows": 1,
                  "filtered": 100
                }
              },
              {
                "table": {
                  "table_name": "products_categories",
                  "access_type": "ref",
                  "possible_keys": ["PRIMARY", "pt"],
                  "key": "PRIMARY",
                  "key_length": "3",
                  "used_key_parts": ["category_id"],
                  "ref": ["const"],
                  "loops": 1,
                  "rows": 104,
                  "cost": 0.0216004,
                  "filtered": 100
                }
              },
              {
                "table": {
                  "table_name": "products",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY", "status", "idx_master_product_id"],
                  "key": "PRIMARY",
                  "key_length": "3",
                  "used_key_parts": ["product_id"],
                  "ref": [
                    "u428615623_ecartifygonje.products_categories.product_id"
                  ],
                  "loops": 104,
                  "rows": 1,
                  "cost": 0.10449056,
                  "filtered": 51.41223526,
                  "attached_condition": "products.master_product_id = 0 and products.company_id in (2,3,4,7,14,15,21,23,25,26,27,28,30,33,34,36,37,38,72,73,74,78,0) and (products.usergroup_ids = '' or find_in_set(0,products.usergroup_ids) or find_in_set(1,products.usergroup_ids)) and products.`status` = 'A' and products.master_product_status = 'A' and products.product_type <> 'D'"
                }
              },
              {
                "table": {
                  "table_name": "companies",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY"],
                  "key": "PRIMARY",
                  "key_length": "4",
                  "used_key_parts": ["company_id"],
                  "ref": ["u428615623_ecartifygonje.products.company_id"],
                  "loops": 53.46872505,
                  "rows": 1,
                  "cost": 0.050282166,
                  "filtered": 100,
                  "attached_condition": "trigcond(companies.`status` = 'A' or products.company_id = 0)"
                }
              },
              {
                "table": {
                  "table_name": "descr1",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY", "product_id"],
                  "key": "PRIMARY",
                  "key_length": "9",
                  "used_key_parts": ["product_id", "lang_code"],
                  "ref": [
                    "u428615623_ecartifygonje.products_categories.product_id",
                    "const"
                  ],
                  "loops": 53.46872505,
                  "rows": 1,
                  "cost": 0.059293366,
                  "filtered": 100,
                  "attached_condition": "trigcond(descr1.lang_code = 'de')"
                }
              },
              {
                "table": {
                  "table_name": "prices",
                  "access_type": "ref",
                  "possible_keys": [
                    "usergroup",
                    "product_id",
                    "lower_limit",
                    "usergroup_id"
                  ],
                  "key": "product_id",
                  "key_length": "3",
                  "used_key_parts": ["product_id"],
                  "ref": [
                    "u428615623_ecartifygonje.products_categories.product_id"
                  ],
                  "loops": 53.46872505,
                  "rows": 1,
                  "cost": 0.052865924,
                  "filtered": 88.3334198,
                  "attached_condition": "prices.lower_limit = 1 and prices.usergroup_id in (0,0,1)",
                  "using_index": true
                }
              },
              {
                "table": {
                  "table_name": "war_sum_amount",
                  "access_type": "ref",
                  "possible_keys": ["PRIMARY"],
                  "key": "PRIMARY",
                  "key_length": "3",
                  "used_key_parts": ["product_id"],
                  "ref": [
                    "u428615623_ecartifygonje.products_categories.product_id"
                  ],
                  "loops": 47.23075472,
                  "rows": 1,
                  "cost": 0.046376569,
                  "filtered": 100
                }
              },
              {
                "table": {
                  "table_name": "warehouses_destination_products_amount",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY", "idx_storefront_id"],
                  "key": "PRIMARY",
                  "key_length": "9",
                  "used_key_parts": [
                    "product_id",
                    "destination_id",
                    "storefront_id"
                  ],
                  "ref": [
                    "u428615623_ecartifygonje.products_categories.product_id",
                    "const",
                    "const"
                  ],
                  "loops": 47.23075472,
                  "rows": 1,
                  "cost": 0.043064276,
                  "filtered": 100,
                  "attached_condition": "trigcond(case products.is_stock_split_by_warehouses when 'Y' then warehouses_destination_products_amount.amount else products.amount end > 0 or products.tracking = 'D')"
                }
              },
              {
                "table": {
                  "table_name": "master_products_storefront_offers_count",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY", "idx_storefront_id"],
                  "key": "PRIMARY",
                  "key_length": "8",
                  "used_key_parts": ["product_id", "storefront_id"],
                  "ref": [
                    "u428615623_ecartifygonje.products_categories.product_id",
                    "const"
                  ],
                  "loops": 47.23075472,
                  "rows": 1,
                  "cost": 0.043064276,
                  "filtered": 100,
                  "attached_condition": "trigcond(products.company_id > 0 or master_products_storefront_offers_count.count > 0) and trigcond(master_products_storefront_offers_count.product_id = products_categories.product_id)"
                }
              }
            ]
          }
        }
      }
    }
  }
}