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 (
    351555, 355162, 357394, 359184, 350155, 
    350822, 352138, 352551, 353205, 353705, 
    355264, 355494, 355511, 356599, 357117, 
    351427, 354504, 355815, 356042, 350248, 
    352377, 352385, 353616, 354889, 356579, 
    357370, 357926, 358666, 349777, 353499, 
    353646, 356614, 357549, 349785, 349888, 
    350077, 352767, 354543, 356178, 350143, 
    351571, 352945, 354660, 354668, 357354, 
    349767, 350509, 353486, 353670, 357359, 
    357723, 358183, 359144, 350763, 351206, 
    351767, 352020, 352137, 352527, 356666, 
    349728, 349948, 351158, 351170, 352579, 
    353241, 354303, 355534, 356941, 359404, 
    350303, 350864, 350882, 351133, 351147, 
    351240, 351688, 353596, 353740, 354186, 
    356498, 356823, 357051, 357688, 358111, 
    349753, 350085, 351726, 353130, 353408, 
    353680, 353903, 356642, 357309, 349850, 
    350427, 350590, 356779, 350837, 351809
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00283

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 (351555,355162,357394,359184,350155,350822,352138,352551,353205,353705,355264,355494,355511,356599,357117,351427,354504,355815,356042,350248,352377,352385,353616,354889,356579,357370,357926,358666,349777,353499,353646,356614,357549,349785,349888,350077,352767,354543,356178,350143,351571,352945,354660,354668,357354,349767,350509,353486,353670,357359,357723,358183,359144,350763,351206,351767,352020,352137,352527,356666,349728,349948,351158,351170,352579,353241,354303,355534,356941,359404,350303,350864,350882,351133,351147,351240,351688,353596,353740,354186,356498,356823,357051,357688,358111,349753,350085,351726,353130,353408,353680,353903,356642,357309,349850,350427,350590,356779,350837,351809))"
          }
        },
        {
          "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')))"
          }
        }
      ]
    }
  }
}