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 = 265 
WHERE 
  cscart_products_categories.product_id IN (
    10065, 10066, 10067, 10068, 10069, 10070, 
    10071, 10072, 10073, 10074, 10075, 
    10076, 10077, 10078, 10079, 10080, 
    10081, 10082, 10083, 10084, 10085, 
    10086, 10087, 10088, 10089, 10090, 
    10091, 10092, 10093, 10094, 10095, 
    10096, 10097, 10098, 10099, 10100, 
    10101, 10102, 10103, 10104, 10105, 
    10106, 10107, 10108, 10109, 10110, 
    10111, 10420, 10421, 10422, 10423, 
    10424, 10425, 10426, 10427, 10428, 
    10429, 10430, 10431, 10432, 10433, 
    10434, 10435, 10436, 10437, 10438, 
    10439, 10440, 10441, 10442, 10443, 
    10444, 10445, 10446, 10447, 10448, 
    10449, 10450, 10451, 10452, 10453, 
    10454, 10455, 10456, 10457, 10458, 
    10459, 10460, 10461, 10462, 10463, 
    10464, 10465, 10466, 10467, 10468
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00301

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "68.63"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.72"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 40,
            "rows_produced_per_join": 1,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "4.54",
              "eval_cost": "0.16",
              "prefix_cost": "4.70",
              "data_read_per_join": "6K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`gaseus`.`cscart_categories`.`storefront_id` in (0,1)) and ((`gaseus`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`gaseus`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`gaseus`.`cscart_categories`.`usergroup_ids`))) and (`gaseus`.`cscart_categories`.`status` in ('A','H')))"
          }
        },
        {
          "table": {
            "table_name": "cscart_products_categories",
            "access_type": "ref",
            "possible_keys": [
              "PRIMARY",
              "pt"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "category_id"
            ],
            "key_length": "3",
            "ref": [
              "gaseus.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 110,
            "rows_produced_per_join": 1,
            "filtered": "0.98",
            "index_condition": "(`gaseus`.`cscart_products_categories`.`product_id` in (10065,10066,10067,10068,10069,10070,10071,10072,10073,10074,10075,10076,10077,10078,10079,10080,10081,10082,10083,10084,10085,10086,10087,10088,10089,10090,10091,10092,10093,10094,10095,10096,10097,10098,10099,10100,10101,10102,10103,10104,10105,10106,10107,10108,10109,10110,10111,10420,10421,10422,10423,10424,10425,10426,10427,10428,10429,10430,10431,10432,10433,10434,10435,10436,10437,10438,10439,10440,10441,10442,10443,10444,10445,10446,10447,10448,10449,10450,10451,10452,10453,10454,10455,10456,10457,10458,10459,10460,10461,10462,10463,10464,10465,10466,10467,10468))",
            "cost_info": {
              "read_cost": "44.00",
              "eval_cost": "0.17",
              "prefix_cost": "66.30",
              "data_read_per_join": "27"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "link_type"
            ]
          }
        },
        {
          "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",
              "gaseus.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.43",
              "eval_cost": "0.17",
              "prefix_cost": "66.91",
              "data_read_per_join": "27"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}