SELECT 
  id_path 
FROM 
  cscart_categories 
WHERE 
  category_id IN (1547, 1607, 1703, 1757, 1892, 2002)

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_categories",
      "access_type": "range",
      "possible_keys": ["PRIMARY", "p_category_id"],
      "key": "p_category_id",
      "key_length": "3",
      "used_key_parts": ["category_id"],
      "rows": 6,
      "filtered": 100,
      "index_condition": "cscart_categories.category_id in (1547,1607,1703,1757,1892,2002)"
    }
  }
}

Result