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 (
    4065, 4142, 4143, 4144, 4145, 4146, 4147, 
    4148, 4195, 4196, 4197, 4198, 4199, 
    4200, 4201, 6716, 6715, 3117, 3119, 
    3127, 3133, 3141, 3142, 6674, 6680, 
    6692, 6693, 6701, 6707, 1417, 1393, 
    1394, 1395, 1396, 1397, 1398, 1399, 
    1400, 1401, 1402, 1403, 1404, 1405, 
    1406, 1407, 1408, 1409, 1410, 1411, 
    1412, 1413, 1414, 1415, 1416, 5107, 
    5108, 5109, 5110, 5111, 5112, 5113, 
    5114, 5115, 5116, 5117, 5118, 5119, 
    5120, 5121, 5122, 5123, 5124, 5125, 
    5126, 5127, 5128, 5129, 5130, 340, 341, 
    342, 343, 344, 345, 346, 412, 413, 414, 
    1366, 1367, 1368, 1369, 1370, 1371, 
    1372, 1373
  ) 
GROUP BY 
  cscart_products_categories.product_id

Query time 0.00300

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "61.28"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "1.85"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_categories",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "c_status",
              "p_category_id"
            ],
            "rows_examined_per_scan": 46,
            "rows_produced_per_join": 1,
            "filtered": "4.00",
            "cost_info": {
              "read_cost": "5.15",
              "eval_cost": "0.18",
              "prefix_cost": "5.33",
              "data_read_per_join": "7K"
            },
            "used_columns": [
              "category_id",
              "storefront_id",
              "usergroup_ids",
              "status"
            ],
            "attached_condition": "((`test2_gaseus`.`cscart_categories`.`storefront_id` in (0,1)) and ((`test2_gaseus`.`cscart_categories`.`usergroup_ids` = '') or (0 <> find_in_set(0,`test2_gaseus`.`cscart_categories`.`usergroup_ids`)) or (0 <> find_in_set(1,`test2_gaseus`.`cscart_categories`.`usergroup_ids`))) and (`test2_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": [
              "test2_gaseus.cscart_categories.category_id"
            ],
            "rows_examined_per_scan": 83,
            "rows_produced_per_join": 1,
            "filtered": "1.21",
            "index_condition": "(`test2_gaseus`.`cscart_products_categories`.`product_id` in (4065,4142,4143,4144,4145,4146,4147,4148,4195,4196,4197,4198,4199,4200,4201,6716,6715,3117,3119,3127,3133,3141,3142,6674,6680,6692,6693,6701,6707,1417,1393,1394,1395,1396,1397,1398,1399,1400,1401,1402,1403,1404,1405,1406,1407,1408,1409,1410,1411,1412,1413,1414,1415,1416,5107,5108,5109,5110,5111,5112,5113,5114,5115,5116,5117,5118,5119,5120,5121,5122,5123,5124,5125,5126,5127,5128,5129,5130,340,341,342,343,344,345,346,412,413,414,1366,1367,1368,1369,1370,1371,1372,1373))",
            "cost_info": {
              "read_cost": "38.18",
              "eval_cost": "0.19",
              "prefix_cost": "58.78",
              "data_read_per_join": "29"
            },
            "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",
              "test2_gaseus.cscart_products_categories.product_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 1,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "0.46",
              "eval_cost": "0.19",
              "prefix_cost": "59.43",
              "data_read_per_join": "29"
            },
            "used_columns": [
              "product_id",
              "category_id",
              "position"
            ]
          }
        }
      ]
    }
  }
}