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, 
  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 = 'en' 
  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_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 (304) 
  AND (
    companies.status IN ('A') 
    OR products.company_id = 0
  ) 
  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 0.02585

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 29.89213443,
    "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": 4586,
                  "cost": 0.88583574,
                  "filtered": 100
                }
              },
              {
                "table": {
                  "table_name": "products",
                  "access_type": "eq_ref",
                  "possible_keys": [
                    "PRIMARY",
                    "status",
                    "idx_master_product_id",
                    "wdbi_master_product_status_master_product_id_produc_46b93429beec",
                    "wdbi_master_product_id_master_product_status_produc_611007cab252",
                    "wdbi_master_product_id_master_product_status_produc_37d8c9a2112a",
                    "wdbi_master_product_id_master_product_status_status_1d4dcd83320a",
                    "wdbi_master_product_id_master_product_status_produc_909a0cf2d55b",
                    "wdbi_master_product_id_master_product_status_status_ff7ba2ae2fb0"
                  ],
                  "key": "PRIMARY",
                  "key_length": "3",
                  "used_key_parts": ["product_id"],
                  "ref": [
                    "u985510652_ecartify_abhi.products_categories.product_id"
                  ],
                  "loops": 4586,
                  "rows": 1,
                  "cost": 7.85875304,
                  "filtered": 100,
                  "attached_condition": "products.master_product_id = 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": "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": [
                    "u985510652_ecartify_abhi.products_categories.product_id",
                    "const"
                  ],
                  "loops": 4586,
                  "rows": 1,
                  "cost": 4.10272104,
                  "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)"
                }
              },
              {
                "table": {
                  "table_name": "companies",
                  "access_type": "eq_ref",
                  "possible_keys": ["PRIMARY"],
                  "key": "PRIMARY",
                  "key_length": "4",
                  "used_key_parts": ["company_id"],
                  "ref": ["u985510652_ecartify_abhi.products.company_id"],
                  "loops": 4586,
                  "rows": 1,
                  "cost": 4.10272104,
                  "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": [
                    "u985510652_ecartify_abhi.products_categories.product_id",
                    "const"
                  ],
                  "loops": 4586,
                  "rows": 1,
                  "cost": 7.85875304,
                  "filtered": 100,
                  "attached_condition": "trigcond(descr1.lang_code = 'en')"
                }
              },
              {
                "table": {
                  "table_name": "prices",
                  "access_type": "ref",
                  "possible_keys": [
                    "usergroup",
                    "product_id",
                    "lower_limit",
                    "usergroup_id",
                    "wdbi_product_id_lower_limit_usergroup_id_price_eff1727beeef",
                    "wdbi_usergroup_id_lower_limit_product_id_92b7e8f6a250",
                    "wdbi_product_id_lower_limit_usergroup_id_price_perc_3b2301d551d0",
                    "wdbi_lower_limit_usergroup_id_product_id_b93629431718"
                  ],
                  "key": "product_id",
                  "key_length": "3",
                  "used_key_parts": ["product_id"],
                  "ref": [
                    "u985510652_ecartify_abhi.products_categories.product_id"
                  ],
                  "loops": 4586,
                  "rows": 1,
                  "cost": 5.08335053,
                  "filtered": 100,
                  "attached_condition": "prices.lower_limit = 1 and prices.usergroup_id in (0,0,1)",
                  "using_index": true
                }
              }
            ]
          }
        }
      }
    }
  }
}