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 = 266 
WHERE 
  cscart_products_categories.product_id IN (
    430938, 431208, 431241, 431335, 431447, 
    430727, 430973, 430985, 431292, 430752, 
    430757, 430942, 431383, 431488, 431502, 
    430978, 431017, 431210, 431236, 431330, 
    430719, 430929, 431227, 431235, 431427, 
    431466, 430630, 430632, 431263, 431482, 
    430943, 431040, 430955, 431415, 431018, 
    431069, 431364, 430693, 430971, 431361, 
    431378, 381708, 431281, 431421, 431302, 
    431385, 431285, 431369, 430717, 430785, 
    431212, 431402, 430725, 430833, 430941, 
    431086, 430736, 430987, 431384, 430724, 
    430733, 431229, 431300, 431377, 431472, 
    430721, 431223, 431253, 431181, 431454, 
    430682, 430951, 430956, 431081, 431431, 
    431225, 431468, 381715, 431387, 431446, 
    430716, 431401, 431438, 431143, 431382, 
    431412, 431430, 431058, 431170, 430945, 
    431215, 431460, 431224, 431294, 431310, 
    431312, 431367, 431450, 339768, 430731
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00181

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 (430938,431208,431241,431335,431447,430727,430973,430985,431292,430752,430757,430942,431383,431488,431502,430978,431017,431210,431236,431330,430719,430929,431227,431235,431427,431466,430630,430632,431263,431482,430943,431040,430955,431415,431018,431069,431364,430693,430971,431361,431378,381708,431281,431421,431302,431385,431285,431369,430717,430785,431212,431402,430725,430833,430941,431086,430736,430987,431384,430724,430733,431229,431300,431377,431472,430721,431223,431253,431181,431454,430682,430951,430956,431081,431431,431225,431468,381715,431387,431446,430716,431401,431438,431143,431382,431412,431430,431058,431170,430945,431215,431460,431224,431294,431310,431312,431367,431450,339768,430731))"
          }
        },
        {
          "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')))"
          }
        }
      ]
    }
  }
}