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 (
    431070, 431397, 431433, 431255, 431389, 
    431268, 431398, 430783, 431432, 431443, 
    431305, 431306, 430775, 431399, 431493, 
    431386, 431417, 430784, 430967, 431444, 
    431272, 435512, 431016, 431416, 431484, 
    430776, 431254, 431490, 435513, 430763, 
    431371, 431461, 431216, 431318, 431319, 
    431271, 435515, 431269, 431372, 431373, 
    431173, 435514, 430729, 431267, 431270, 
    387051, 435516, 435517, 435518, 432250
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00201

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "141.08"
    },
    "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": 50,
            "rows_produced_per_join": 50,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "11.08",
              "eval_cost": "10.00",
              "prefix_cost": "21.08",
              "data_read_per_join": "800"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ],
            "attached_condition": "(`webmarco`.`cscart_products_categories`.`product_id` in (431070,431397,431433,431255,431389,431268,431398,430783,431432,431443,431305,431306,430775,431399,431493,431386,431417,430784,430967,431444,431272,435512,431016,431416,431484,430776,431254,431490,435513,430763,431371,431461,431216,431318,431319,431271,435515,431269,431372,431373,431173,435514,430729,431267,431270,387051,435516,435517,435518,432250))"
          }
        },
        {
          "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": 50,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "50.00",
              "eval_cost": "10.00",
              "prefix_cost": "81.08",
              "data_read_per_join": "800"
            },
            "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": 2,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "50.00",
              "eval_cost": "0.50",
              "prefix_cost": "141.08",
              "data_read_per_join": "14K"
            },
            "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')))"
          }
        }
      ]
    }
  }
}