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 (
    350592, 351862, 354203, 356480, 356560, 
    352897, 356801, 358945, 349757, 356497, 
    356655, 353178, 356621, 350319, 357585, 
    359008, 359423, 357930, 352714, 356443, 
    356820, 356985, 352282, 352085, 354417, 
    355651, 350568, 357383, 353410, 354653, 
    350662, 350975, 351747, 351892, 352001, 
    352747, 357301, 350152, 350702, 352610, 
    353056, 352021, 354389, 354942, 359333, 
    350645, 352146, 351489, 351559, 354382, 
    353005, 353543, 354867, 356810, 350934, 
    358064, 350921, 351928, 357077, 359076, 
    351691, 354804, 355599, 354563, 357575, 
    350464, 349744, 354771, 349701, 349734, 
    349789, 352000, 352373, 352559, 354400, 
    355170, 357736, 358536, 358989, 359320, 
    350473, 353799, 358182, 352578, 353895, 
    356669, 349735, 353312, 353424, 351936, 
    358007, 350147, 350705, 352078, 354094, 
    354802, 356694, 351931, 353703, 350055
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00190

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 (350592,351862,354203,356480,356560,352897,356801,358945,349757,356497,356655,353178,356621,350319,357585,359008,359423,357930,352714,356443,356820,356985,352282,352085,354417,355651,350568,357383,353410,354653,350662,350975,351747,351892,352001,352747,357301,350152,350702,352610,353056,352021,354389,354942,359333,350645,352146,351489,351559,354382,353005,353543,354867,356810,350934,358064,350921,351928,357077,359076,351691,354804,355599,354563,357575,350464,349744,354771,349701,349734,349789,352000,352373,352559,354400,355170,357736,358536,358989,359320,350473,353799,358182,352578,353895,356669,349735,353312,353424,351936,358007,350147,350705,352078,354094,354802,356694,351931,353703,350055))"
          }
        },
        {
          "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')))"
          }
        }
      ]
    }
  }
}