SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (
    1, 16, 17, 25, 26, 33, 34, 35, 36, 46, 67, 
    107, 234, 235, 239, 240, 243, 257, 261, 
    304, 306
  )

Query time 0.00049

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": 21,
      "filtered": 100,
      "index_condition": "cscart_categories.category_id in (1,16,17,25,26,33,34,35,36,46,67,107,234,235,239,240,243,257,261,304,306)"
    }
  }
}