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, 
  IF(
    shared_descr.product_id IS NOT NULL, 
    shared_descr.product, descr1.product
  ) as product, 
  companies.company as company_name, 
  SUM(
    cscart_also_bought_products.amount
  ) amnt, 
  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 
FROM 
  cscart_products as products 
  LEFT JOIN cscart_product_descriptions as descr1 ON descr1.product_id = products.product_id 
  AND descr1.lang_code = 'ru' 
  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_ult_product_descriptions shared_descr ON shared_descr.product_id = products.product_id 
  AND shared_descr.company_id = 1 
  AND shared_descr.lang_code = 'ru' 
  LEFT JOIN cscart_also_bought_products ON cscart_also_bought_products.related_id = products.product_id 
WHERE 
  1 
  AND companies.status IN ('A') 
  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 cscart_also_bought_products.product_id IN (91) 
GROUP BY 
  product_id 
ORDER BY 
  SUM(
    cscart_also_bought_products.amount
  ) desc, 
  products.product_id ASC 
LIMIT 
  0, 15

Query time 0.00517

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "17.24"
    },
    "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": "companies",
                "access_type": "system",
                "possible_keys": [
                  "PRIMARY"
                ],
                "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": "0.00",
                  "data_read_per_join": "6K"
                },
                "used_columns": [
                  "company_id",
                  "status",
                  "company"
                ]
              }
            },
            {
              "table": {
                "table_name": "shared_descr",
                "access_type": "system",
                "possible_keys": [
                  "PRIMARY",
                  "product_id",
                  "company_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": "5K"
                },
                "used_columns": [
                  "product_id",
                  "lang_code",
                  "company_id",
                  "product"
                ]
              }
            },
            {
              "table": {
                "table_name": "cscart_also_bought_products",
                "access_type": "ref",
                "possible_keys": [
                  "PRIMARY"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "const"
                ],
                "rows_examined_per_scan": 36,
                "rows_produced_per_join": 36,
                "filtered": "100.00",
                "index_condition": "(`testdobroded`.`cscart_also_bought_products`.`related_id` is not null)",
                "cost_info": {
                  "read_cost": "9.00",
                  "eval_cost": "3.60",
                  "prefix_cost": "12.60",
                  "data_read_per_join": "576"
                },
                "used_columns": [
                  "product_id",
                  "related_id",
                  "amount"
                ]
              }
            },
            {
              "table": {
                "table_name": "products",
                "access_type": "eq_ref",
                "possible_keys": [
                  "PRIMARY",
                  "status"
                ],
                "key": "PRIMARY",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "testdobroded.cscart_also_bought_products.related_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 1,
                "filtered": "5.00",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.18",
                  "prefix_cost": "16.20",
                  "data_read_per_join": "17K"
                },
                "used_columns": [
                  "product_id",
                  "product_type",
                  "status",
                  "company_id",
                  "usergroup_ids",
                  "parent_product_id"
                ],
                "attached_condition": "((`testdobroded`.`products`.`company_id` = '1') and ((`testdobroded`.`products`.`usergroup_ids` = '') or (0 <> find_in_set(0,`testdobroded`.`products`.`usergroup_ids`)) or (0 <> find_in_set(1,`testdobroded`.`products`.`usergroup_ids`))) and (`testdobroded`.`products`.`status` = 'A'))"
              }
            },
            {
              "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": [
                  "testdobroded.cscart_also_bought_products.related_id",
                  "const"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 1,
                "filtered": "100.00",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.18",
                  "prefix_cost": "16.38",
                  "data_read_per_join": "10K"
                },
                "used_columns": [
                  "product_id",
                  "lang_code",
                  "product"
                ]
              }
            },
            {
              "table": {
                "table_name": "products_categories",
                "access_type": "ref",
                "possible_keys": [
                  "PRIMARY",
                  "pt"
                ],
                "key": "pt",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "testdobroded.cscart_also_bought_products.related_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 1,
                "filtered": "100.00",
                "cost_info": {
                  "read_cost": "0.45",
                  "eval_cost": "0.18",
                  "prefix_cost": "17.01",
                  "data_read_per_join": "28"
                },
                "used_columns": [
                  "product_id",
                  "category_id"
                ]
              }
            },
            {
              "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": [
                  "testdobroded.products_categories.category_id"
                ],
                "rows_examined_per_scan": 1,
                "rows_produced_per_join": 0,
                "filtered": "5.00",
                "cost_info": {
                  "read_cost": "0.00",
                  "eval_cost": "0.01",
                  "prefix_cost": "17.19",
                  "data_read_per_join": "422"
                },
                "used_columns": [
                  "category_id",
                  "usergroup_ids",
                  "status",
                  "storefront_id"
                ],
                "attached_condition": "(((`testdobroded`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`testdobroded`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`testdobroded`.`cscart_categories`.`usergroup_ids`))) and (`testdobroded`.`cscart_categories`.`status` in ('A','H')) and (`testdobroded`.`cscart_categories`.`storefront_id` in (0,1)))"
              }
            },
            {
              "table": {
                "table_name": "prices",
                "access_type": "ref",
                "possible_keys": [
                  "usergroup",
                  "product_id",
                  "lower_limit",
                  "usergroup_id"
                ],
                "key": "usergroup",
                "used_key_parts": [
                  "product_id"
                ],
                "key_length": "3",
                "ref": [
                  "testdobroded.cscart_also_bought_products.related_id"
                ],
                "rows_examined_per_scan": 3,
                "rows_produced_per_join": 0,
                "filtered": "37.21",
                "using_index": true,
                "cost_info": {
                  "read_cost": "0.02",
                  "eval_cost": "0.01",
                  "prefix_cost": "17.24",
                  "data_read_per_join": "2"
                },
                "used_columns": [
                  "product_id",
                  "lower_limit",
                  "usergroup_id"
                ],
                "attached_condition": "((`testdobroded`.`prices`.`lower_limit` = 1) and (`testdobroded`.`prices`.`usergroup_id` in (0,0,1)))"
              }
            }
          ]
        }
      }
    }
  }
}