SELECT 
  cscart_products_categories.product_id, 
  GROUP_CONCAT(
    IF(
      cscart_products_categories.link_type = "M", 
      CONCAT(
        cscart_products_categories.category_id, 
        "M"
      ), 
      cscart_products_categories.category_id
    )
  ) AS category_ids, 
  product_position_source.position AS position 
FROM 
  cscart_products_categories 
  INNER JOIN cscart_categories ON cscart_categories.category_id = cscart_products_categories.category_id 
  AND cscart_categories.storefront_id IN (0, 1) 
  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_products_categories AS product_position_source ON cscart_products_categories.product_id = product_position_source.product_id 
  AND product_position_source.category_id = 271 
WHERE 
  cscart_products_categories.product_id IN (
    3775, 3776, 3777, 1143, 1139, 1140, 1141, 
    1142, 3681, 3682, 3683, 3684, 3685, 
    4890, 2207, 2208, 2209, 2210, 2211, 
    2212, 2213, 2214, 2215, 2216, 5808, 
    5809, 5810, 5811, 5812, 5813, 5814, 
    5815, 5816, 1654, 1655, 1656, 1657, 
    1658, 1659, 1660, 1661, 1662, 1663, 
    1664, 1665, 1666, 1667, 1668, 1669, 
    1670, 1671, 2220, 2221, 2222, 2223, 
    5353, 5354, 5355, 5356, 5357, 5358, 
    5359, 5360, 5361, 5362, 5363, 5364, 
    5365, 5366, 5367, 5368, 5369, 5370, 
    5820, 5821, 5822, 5823, 5802
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00351

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "68.13"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.36"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 40,
            "rows_produced_per_join": 1,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "4.54",
              "eval_cost": "0.16",
              "prefix_cost": "4.70",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`gaseus`.`cscart_categories`.`storefront_id` in (0,1)) and ((`gaseus`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`gaseus`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`gaseus`.`cscart_categories`.`usergroup_ids`))) and (`gaseus`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "gaseus.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 110,
            "rows_produced_per_join": 1,
            "filtered": "0.77",
            "index_condition": "(`gaseus`.`cscart_products_categories`.`product_id` in (3775,3776,3777,1143,1139,1140,1141,1142,3681,3682,3683,3684,3685,4890,2207,2208,2209,2210,2211,2212,2213,2214,2215,2216,5808,5809,5810,5811,5812,5813,5814,5815,5816,1654,1655,1656,1657,1658,1659,1660,1661,1662,1663,1664,1665,1666,1667,1668,1669,1670,1671,2220,2221,2222,2223,5353,5354,5355,5356,5357,5358,5359,5360,5361,5362,5363,5364,5365,5366,5367,5368,5369,5370,5820,5821,5822,5823,5802))",
            "cost_info": {
              "read_cost": "44.00",
              "eval_cost": "0.14",
              "prefix_cost": "66.30",
              "data_read_per_join": "21"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "table": {
            "table_name": "product_position_source",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id",
              "product_id"
            ],
            "key_length": "6",
            "ref": [
              "const",
              "gaseus.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.34",
              "eval_cost": "0.14",
              "prefix_cost": "66.78",
              "data_read_per_join": "21"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}