SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (
    49, 56, 67, 71, 77, 81, 90, 93, 119, 217, 
    233, 234, 238, 241, 265, 267, 304, 306
  )

Query time 0.00050

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": 18,
      "filtered": 100,
      "index_condition": "cscart_categories.category_id in (49,56,67,71,77,81,90,93,119,217,233,234,238,241,265,267,304,306)"
    }
  }
}