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, 
  COALESCE(
    cscart_master_products_storefront_min_price.price, 
    MIN(
      IF(
        prices.percentage_discount = 0, 
        prices.price, 
        prices.price - (
          prices.price * prices.percentage_discount
        )/ 100
      )
    )
  ) as price, 
  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, 
  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, 
  1 as instock_marker, 
  IF(
    products.product_type = 'C', 
    (
      SELECT 
        MAX(amount) 
      FROM 
        cscart_products 
      WHERE 
        parent_product_id = products.product_id
    ) > 0, 
    IF(
      IF(
        products.tracking = 'O', 
        (
          SELECT 
            MAX(amount) 
          FROM 
            cscart_product_options_inventory s_inventory 
          WHERE 
            s_inventory.product_id = products.product_id
        ) > 0, 
        products.amount > 0
      ), 
      1, 
      IF(products.tracking = 'D', 1, 0)
    )
  ) as instock_sorting 
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, 3) 
  LEFT JOIN cscart_warehouses_sum_products_amount as war_sum_amount ON war_sum_amount.product_id = products.product_id 
  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 = 3 
  LEFT JOIN cscart_master_products_storefront_min_price ON cscart_master_products_storefront_min_price.product_id = prices.product_id 
  AND cscart_master_products_storefront_min_price.storefront_id = 3 
WHERE 
  1 
  AND cscart_categories.category_id IN (
    1521, 
    1522, 
    1523, 
    1524, 
    1525, 
    1526, 
    1578, 
    1579, 
    1580, 
    1581, 
    1582, 
    1583, 
    1584, 
    1585, 
    1586, 
    1587, 
    1588, 
    1589, 
    1590, 
    1591, 
    1592, 
    1593, 
    1594, 
    1595, 
    1633, 
    1634, 
    1635, 
    1636, 
    1637, 
    1638, 
    1639, 
    1640, 
    1641, 
    1642, 
    1643, 
    1644, 
    1645, 
    1646, 
    1647, 
    1648, 
    1649, 
    1650, 
    1651, 
    1652, 
    1653, 
    1654, 
    1655, 
    1656, 
    1657, 
    1658, 
    1659, 
    1660, 
    1661, 
    1662, 
    1663, 
    1664, 
    1665, 
    1666, 
    1667, 
    1668, 
    1669, 
    1670, 
    1671, 
    1672, 
    1677, 
    1678, 
    1679, 
    1680, 
    1681, 
    1682, 
    1683, 
    1684, 
    1685, 
    1686, 
    1687, 
    1688, 
    1689, 
    1690, 
    1691, 
    1692, 
    1693, 
    1694, 
    1695, 
    1696, 
    1697, 
    1698, 
    1699, 
    1700, 
    1701, 
    1702, 
    1703, 
    1704, 
    1705, 
    1706, 
    1707, 
    1708, 
    1709, 
    1710, 
    1711, 
    1712, 
    1713, 
    1714, 
    1715, 
    1716, 
    1717, 
    1718, 
    1719, 
    1720, 
    1721, 
    1722, 
    1723, 
    1724, 
    1725, 
    1726, 
    1727, 
    1728, 
    1729, 
    1730, 
    1731, 
    1732, 
    1733, 
    1734, 
    1735, 
    1736, 
    1737, 
    1738, 
    1739, 
    1740, 
    1741, 
    1742, 
    1743, 
    1744, 
    1745, 
    1746, 
    1747, 
    1748, 
    1749, 
    1750, 
    1751, 
    1752, 
    1753, 
    1754, 
    1755, 
    1756, 
    1757, 
    1758, 
    1759, 
    1760, 
    1761, 
    1762, 
    1763, 
    1764, 
    1765, 
    1766, 
    1767, 
    1768, 
    1769, 
    1770, 
    1771, 
    1772, 
    1773, 
    1774, 
    1775, 
    1776, 
    1777, 
    1778, 
    1779, 
    1780, 
    1781, 
    1782, 
    1783, 
    1784, 
    1785, 
    1786, 
    1787, 
    1788, 
    1789, 
    1790, 
    1791, 
    1792, 
    1793, 
    1794, 
    1795, 
    1796, 
    1797, 
    1798, 
    1799, 
    1800, 
    1801, 
    1802, 
    1803, 
    1804, 
    1805, 
    1806, 
    1807, 
    1808, 
    1809, 
    1810, 
    1811, 
    1812, 
    1813, 
    1814, 
    1815, 
    1816, 
    1817, 
    1818, 
    1819, 
    1820, 
    1821, 
    1822, 
    1823, 
    1824, 
    1825, 
    1826, 
    1827, 
    1828, 
    1829, 
    1830, 
    1831, 
    1832, 
    1833, 
    1834, 
    1835, 
    1836, 
    1837, 
    1838, 
    1934, 
    1958, 
    1959, 
    1960, 
    1961
  ) 
  AND (
    companies.status IN ('A', 'S') 
    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 
  instock_sorting DESC, 
  price asc, 
  products.product_id ASC 
LIMIT 
  0, 20

Query time 0.02022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "75.48"
    },
    "ordering_operation": {
      "using_filesort": true,
      "grouping_operation": {
        "using_temporary_table": true,
        "using_filesort": true,
        "buffer_result": {
          "using_temporary_table": true,
          "nested_loop": [
            {
              "table": {
                "table_name": "war_sum_amount",
                "access_type": "system",
                "possible_keys": [
                  "PRIMARY"
                ],
                "rows_examined_per_scan": 0,
                "rows_produced_per_join": 1,
                "filtered": "0.00",
                "const_row_not_found": true,
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.10",
                  "prefix_cost": "0.00",
                  "data_read_per_join": "16"
                },
                "used_columns": [
                  "product_id"
                ]
              }
            },
            {
              "table": {
                "table_name": "master_products_storefront_offers_count",
                "access_type": "system",
                "possible_keys": [
                  "PRIMARY",
                  "idx_storefront_id"
                ],
                "rows_examined_per_scan": 0,
                "rows_produced_per_join": 1,
                "filtered": "0.00",
                "const_row_not_found": true,
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.10",
                  "prefix_cost": "0.00",
                  "data_read_per_join": "16"
                },
                "used_columns": [
                  "storefront_id",
                  "product_id",
                  "count"
                ]
              }
            },
            {
              "table": {
                "table_name": "cscart_master_products_storefront_min_price",
                "access_type": "system",
                "possible_keys": [
                  "PRIMARY"
                ],
                "rows_examined_per_scan": 0,
                "rows_produced_per_join": 1,
                "filtered": "0.00",
                "const_row_not_found": true,
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.10",
                  "prefix_cost": "0.00",
                  "data_read_per_join": "16"
                },
                "used_columns": [
                  "storefront_id",
                  "product_id",
                  "price"
                ]
              }
            },
            {
              "table": {
                "table_name": "products_categories",
                "access_type": "range",
                "possible_keys": [
                  "PRIMARY",
                  "pt"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "category_id"
                ],
                "key_length": "3",
                "rows_examined_per_scan": 231,
                "rows_produced_per_join": 231,
                "filtered": "100.00",
                "using_index": true,
                "cost_info": {
                  "read_cost": "24.80",
                  "eval_cost": "23.10",
                  "prefix_cost": "47.90",
                  "data_read_per_join": "3K"
                },
                "used_columns": [
                  "product_id",
                  "category_id"
                ],
                "attached_condition": "(`s2cart`.`products_categories`.`category_id` in (1521,1522,1523,1524,1525,1526,1578,1579,1580,1581,1582,1583,1584,1585,1586,1587,1588,1589,1590,1591,1592,1593,1594,1595,1633,1634,1635,1636,1637,1638,1639,1640,1641,1642,1643,1644,1645,1646,1647,1648,1649,1650,1651,1652,1653,1654,1655,1656,1657,1658,1659,1660,1661,1662,1663,1664,1665,1666,1667,1668,1669,1670,1671,1672,1677,1678,1679,1680,1681,1682,1683,1684,1685,1686,1687,1688,1689,1690,1691,1692,1693,1694,1695,1696,1697,1698,1699,1700,1701,1702,1703,1704,1705,1706,1707,1708,1709,1710,1711,1712,1713,1714,1715,1716,1717,1718,1719,1720,1721,1722,1723,1724,1725,1726,1727,1728,1729,1730,1731,1732,1733,1734,1735,1736,1737,1738,1739,1740,1741,1742,1743,1744,1745,1746,1747,1748,1749,1750,1751,1752,1753,1754,1755,1756,1757,1758,1759,1760,1761,1762,1763,1764,1765,1766,1767,1768,1769,1770,1771,1772,1773,1774,1775,1776,1777,1778,1779,1780,1781,1782,1783,1784,1785,1786,1787,1788,1789,1790,1791,1792,1793,1794,1795,1796,1797,1798,1799,1800,1801,1802,1803,1804,1805,1806,1807,1808,1809,1810,1811,1812,1813,1814,1815,1816,1817,1818,1819,1820,1821,1822,1823,1824,1825,1826,1827,1828,1829,1830,1831,1832,1833,1834,1835,1836,1837,1838,1934,1958,1959,1960,1961))"
              }
            },
            {
              "table": {
                "table_name": "products",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY",
                  "status",
                  "idx_master_product_id"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "s2cart.products_categories.product_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 20,
                "filtered": "8.72",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "2.01",
                  "prefix_cost": "71.00",
                  "data_read_per_join": "154K"
                },
                "used_columns": [
                  "product_id",
                  "product_type",
                  "status",
                  "company_id",
                  "amount",
                  "usergroup_ids",
                  "tracking",
                  "age_verification",
                  "age_limit",
                  "parent_product_id",
                  "master_product_id",
                  "master_product_status",
                  "master_product_offers_count"
                ],
                "attached_condition": "((`s2cart`.`products`.`master_product_id` = 0) and ((`s2cart`.`products`.`usergroup_ids` = '') or (0 <> find_in_set(0,`s2cart`.`products`.`usergroup_ids`)) or (0 <> find_in_set(1,`s2cart`.`products`.`usergroup_ids`))) and (`s2cart`.`products`.`status` = 'A') and (`s2cart`.`products`.`master_product_status` = 'A') and ((`s2cart`.`products`.`company_id` > 0) or <cache>((NULL > 0))) and (`s2cart`.`products`.`product_type` <> 'D'))"
              }
            },
            {
              "table": {
                "table_name": "companies",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "company_id"
                ],
                "key_length": "4",
                "ref": [
                  "s2cart.products.company_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 20,
                "filtered": "100.00",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "2.01",
                  "prefix_cost": "73.01",
                  "data_read_per_join": "187K"
                },
                "used_columns": [
                  "company_id",
                  "status",
                  "company"
                ],
                "attached_condition": "<if>(found_match(companies), ((`s2cart`.`companies`.`status` in ('A','S')) or (`s2cart`.`products`.`company_id` = 0)), true)"
              }
            },
            {
              "table": {
                "table_name": "cscart_categories",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY",
                  "c_status",
                  "p_category_id"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "category_id"
                ],
                "key_length": "3",
                "ref": [
                  "s2cart.products_categories.category_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 1,
                "filtered": "5.00",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.10",
                  "prefix_cost": "75.02",
                  "data_read_per_join": "3K"
                },
                "used_columns": [
                  "category_id",
                  "usergroup_ids",
                  "status",
                  "age_verification",
                  "age_limit",
                  "parent_age_verification",
                  "parent_age_limit",
                  "storefront_id"
                ],
                "attached_condition": "(((`s2cart`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`s2cart`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`s2cart`.`cscart_categories`.`usergroup_ids`))) and (`s2cart`.`cscart_categories`.`status` in ('A','H')) and (`s2cart`.`cscart_categories`.`storefront_id` in (0,3)))"
              }
            },
            {
              "table": {
                "table_name": "descr1",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY",
                  "product_id"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "product_id",
                  "lang_code"
                ],
                "key_length": "9",
                "ref": [
                  "s2cart.products_categories.product_id",
                  "const"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 1,
                "filtered": "100.00",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.10",
                  "prefix_cost": "75.12",
                  "data_read_per_join": "7K"
                },
                "used_columns": [
                  "product_id",
                  "lang_code",
                  "product"
                ]
              }
            },
            {
              "table": {
                "table_name": "prices",
                "access_type": "ref",
                "possible_keys": [
                  "usergroup",
                  "product_id",
                  "lower_limit",
                  "usergroup_id"
                ],
                "key": "product_id",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "s2cart.products_categories.product_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 1,
                "filtered": "100.00",
                "cost_info": {
                  "read_cost": "0.25",
                  "eval_cost": "0.10",
                  "prefix_cost": "75.48",
                  "data_read_per_join": "24"
                },
                "used_columns": [
                  "product_id",
                  "price",
                  "percentage_discount",
                  "lower_limit",
                  "usergroup_id"
                ],
                "attached_condition": "((`s2cart`.`prices`.`lower_limit` = 1) and (`s2cart`.`prices`.`usergroup_id` in (0,0,1)))"
              }
            }
          ],
          "select_list_subqueries": [
            {
              "dependent": true,
              "cacheable": false,
              "query_block": {
                "select_id": 3,
                "message": "no matching row in const table"
              }
            },
            {
              "dependent": true,
              "cacheable": false,
              "query_block": {
                "select_id": 2,
                "cost_info": {
                  "query_cost": "31651.29"
                },
                "table": {
                  "table_name": "cscart_products",
                  "access_type": "ALL",
                  "possible_keys": [
                    "idx_parent_product_id"
                  ],
                  "rows_examined_per_scan": 270845,
                  "rows_produced_per_join": 27084,
                  "filtered": "10.00",
                  "cost_info": {
                    "read_cost": "4566.79",
                    "eval_cost": "2708.45",
                    "prefix_cost": "31651.29",
                    "data_read_per_join": "203M"
                  },
                  "used_columns": [
                    "amount",
                    "parent_product_id"
                  ],
                  "attached_condition": "(`s2cart`.`cscart_products`.`parent_product_id` = `s2cart`.`products`.`product_id`)"
                }
              }
            }
          ]
        }
      }
    }
  }
}