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 = 1936 
WHERE 
  cscart_products_categories.product_id IN (
    431422, 430983, 431076, 431175, 430957, 
    430965, 431311, 431434, 430659, 430642, 
    430954, 431105, 431166, 431260, 431380, 
    431002, 431004, 431409, 431480, 430963, 
    430964, 431287, 431304, 431346, 431458, 
    430781, 430814, 431015, 431071, 430754, 
    430759, 430798, 430966, 431324, 431217, 
    431362, 431452, 430669, 430944, 431079, 
    431408, 431453, 431481, 430750, 431188, 
    431273, 431352, 431407, 430700, 430727, 
    431222, 431394, 430705, 431001, 430938, 
    430978, 430985, 431208, 430699, 431009, 
    431057, 431241, 431335, 431447, 430757, 
    430942, 430752, 430773, 430973, 431210, 
    431383, 431488, 431502, 430719, 431017, 
    431292, 431427, 431236, 430693, 431040, 
    431235, 431330, 430630, 430943, 431227, 
    431263, 431466, 430632, 430929, 431482, 
    430955, 430971, 431018, 431069, 431364, 
    431415, 431361, 431378, 431281, 431302
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00217

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 (431422,430983,431076,431175,430957,430965,431311,431434,430659,430642,430954,431105,431166,431260,431380,431002,431004,431409,431480,430963,430964,431287,431304,431346,431458,430781,430814,431015,431071,430754,430759,430798,430966,431324,431217,431362,431452,430669,430944,431079,431408,431453,431481,430750,431188,431273,431352,431407,430700,430727,431222,431394,430705,431001,430938,430978,430985,431208,430699,431009,431057,431241,431335,431447,430757,430942,430752,430773,430973,431210,431383,431488,431502,430719,431017,431292,431427,431236,430693,431040,431235,431330,430630,430943,431227,431263,431466,430632,430929,431482,430955,430971,431018,431069,431364,431415,431361,431378,431281,431302))"
          }
        },
        {
          "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')))"
          }
        }
      ]
    }
  }
}