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 = 2910 
WHERE 
  cscart_products_categories.product_id IN (
    351612, 352403, 353662, 354659, 354938, 
    356566, 357755, 357764, 359035, 350308, 
    351499, 352647, 356228, 356851, 357797, 
    358556, 350029, 358941, 349836, 350268, 
    350368, 351541, 354515, 354642, 356094, 
    350097, 351045, 351815, 352157, 352170, 
    352364, 353781, 354169, 355537, 356506, 
    356861, 358535, 354658, 354714, 355301, 
    356246, 350306, 350670, 353632, 349939, 
    352530, 353854, 356306, 356544, 358670, 
    350351, 349772, 349890, 350282, 350342, 
    353127, 354261, 354675, 355540, 356392, 
    358292, 349736, 349887, 349943, 350375, 
    353459, 354694, 354873, 359419, 352803, 
    355567, 351312, 354235, 355500, 355793, 
    356645, 349694, 349826, 351595, 354250, 
    354734, 358441, 359053, 352613, 353085, 
    353938, 354120, 354124, 356294, 357584, 
    359116, 353517, 354432, 354541, 356325, 
    356896, 351436, 355573, 358867, 359228
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00237

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "281.15"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "range",
            "possible_keys": [
              "PRIMARY",
              "link_type",
              "pt"
            ],
            "key": "pt",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "rows_examined_per_scan": 100,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "21.15",
              "eval_cost": "20.00",
              "prefix_cost": "41.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (351612,352403,353662,354659,354938,356566,357755,357764,359035,350308,351499,352647,356228,356851,357797,358556,350029,358941,349836,350268,350368,351541,354515,354642,356094,350097,351045,351815,352157,352170,352364,353781,354169,355537,356506,356861,358535,354658,354714,355301,356246,350306,350670,353632,349939,352530,353854,356306,356544,358670,350351,349772,349890,350282,350342,353127,354261,354675,355540,356392,358292,349736,349887,349943,350375,353459,354694,354873,359419,352803,355567,351312,354235,355500,355793,356645,349694,349826,351595,354250,354734,358441,359053,352613,353085,353938,354120,354124,356294,357584,359116,353517,354432,354541,356325,356896,351436,355573,358867,359228))"
          }
        },
        {
          "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",
              "webmarco.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 100,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "20.00",
              "prefix_cost": "161.15",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        },
        {
          "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": [
              "webmarco.cscart_products_categories.category_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 5,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "100.00",
              "eval_cost": "1.00",
              "prefix_cost": "281.15",
              "data_read_per_join": "29K"
            },
            "used_columns": [
              "category_id",
              "usergroup_ids",
              "status",
              "storefront_id"
            ],
            "attached_condition": "((`webmarco`.`cscart_categories`.`storefront_id` in (0,1)) and ((`webmarco`.`cscart_categories`.`usergroup_ids` = '') or find_in_set(0,`webmarco`.`cscart_categories`.`usergroup_ids`) or find_in_set(1,`webmarco`.`cscart_categories`.`usergroup_ids`)) and (`webmarco`.`cscart_categories`.`status` in ('A','H')))"
          }
        }
      ]
    }
  }
}