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 (
    430732, 430833, 430942, 430985, 431076, 
    431466, 431480, 339768, 387046, 430750, 
    431210, 431219, 431330, 431438, 431452, 
    430719, 431380, 430724, 430987, 431181, 
    431222, 431285, 431377, 431481, 431239, 
    431353, 431387, 381709, 430693, 431229, 
    431241, 431412, 431447, 430632, 430727, 
    431292, 431384, 431385, 431440, 431502, 
    431208, 431236, 430733, 431188, 431281, 
    430721, 430682, 431259, 431224, 431335, 
    431361, 430699, 431421, 430701, 430955, 
    431249, 431253, 431332, 431458, 430951, 
    431040, 431081, 431172, 431402, 430731, 
    430757, 431431, 430945, 431009, 431143, 
    431215, 431263, 431298, 431468, 381715, 
    430736, 431170, 431442, 431455, 431472, 
    381706, 431364, 431401, 431414, 431478, 
    430970, 431180, 431454, 381708, 430941, 
    430954, 431233, 431369, 431378, 431446, 
    430725, 431014, 431213, 431225, 431300
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00230

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 (430732,430833,430942,430985,431076,431466,431480,339768,387046,430750,431210,431219,431330,431438,431452,430719,431380,430724,430987,431181,431222,431285,431377,431481,431239,431353,431387,381709,430693,431229,431241,431412,431447,430632,430727,431292,431384,431385,431440,431502,431208,431236,430733,431188,431281,430721,430682,431259,431224,431335,431361,430699,431421,430701,430955,431249,431253,431332,431458,430951,431040,431081,431172,431402,430731,430757,431431,430945,431009,431143,431215,431263,431298,431468,381715,430736,431170,431442,431455,431472,381706,431364,431401,431414,431478,430970,431180,431454,381708,430941,430954,431233,431369,431378,431446,430725,431014,431213,431225,431300))"
          }
        },
        {
          "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')))"
          }
        }
      ]
    }
  }
}