SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (
    1, 17, 27, 34, 47, 62, 67, 118, 123, 235, 
    238, 249, 257, 261, 306
  )

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "rows": 15,
      "filtered": 100,
      "index_condition": "cscart_categories.category_id in (1,17,27,34,47,62,67,118,123,235,238,249,257,261,306)"
    }
  }
}